Fix mathematically incorrect statements about empty sets in set documentation

xml/System.Collections.Generic/HashSet`1.xml

@@ -1594,7 +1594,7 @@ The following example demonstrates how to merge two disparate sets. This example
           <format type="text/markdown"><![CDATA[
 
 ## Remarks
- An empty set is a proper subset of any other collection. Therefore, this method returns `true` if the collection represented by the current <xref:System.Collections.Generic.HashSet%601> object is empty unless the `other` parameter is also an empty set.
+ An empty set is a subset of any other collection. Therefore, this method returns `true` if the collection represented by the current <xref:System.Collections.Generic.HashSet%601> object is empty unless the `other` parameter is also an empty set.
 
  This method always returns `false` if <xref:System.Collections.Generic.HashSet%601.Count%2A> is greater than or equal to the number of elements in `other`.
 
@@ -1676,7 +1676,7 @@ The following example demonstrates how to merge two disparate sets. This example
           <format type="text/markdown"><![CDATA[
 
 ## Remarks
- An empty set is a proper superset of any other collection. Therefore, this method returns `true` if the collection represented by the `other` parameter is empty unless the current <xref:System.Collections.Generic.HashSet%601> collection is also empty.
+ An empty set is a subset of any other collection. Therefore, this method returns `true` if the collection represented by the `other` parameter is empty unless the current <xref:System.Collections.Generic.HashSet%601> collection is also empty.
 
  This method always returns `false` if <xref:System.Collections.Generic.HashSet%601.Count%2A> is less than or equal to the number of elements in `other`.
 

xml/System.Collections.Generic/ISet`1.xml

@@ -285,7 +285,7 @@
 ## Remarks  
  If the current set is a proper subset of `other`, `other` must have at least one element that the current set does not have.  
   
- An empty set is a proper subset of any other collection. Therefore, this method returns `true` if the current set is empty, unless the `other` parameter is also an empty set.  
+ An empty set is a subset of any other collection. Therefore, this method returns `true` if the current set is empty, unless the `other` parameter is also an empty set.  
   
  This method always returns `false` if the current set has more or the same number of elements than `other`.  
   
@@ -346,7 +346,7 @@
 ## Remarks  
  If the current set is a proper superset of `other`, the current set must have at least one element that `other` does not have.  
   
- An empty set is a proper superset of any other collection. Therefore, this method returns `true` if the collection represented by the `other` parameter is empty, unless the current set is also empty.  
+ An empty set is a subset of any other collection. Therefore, this method returns `true` if the collection represented by the `other` parameter is empty, unless the current set is also empty.  
   
  This method always returns `false` if the number of elements in the current set is less than or equal to the number of elements in `other`.  
   

xml/System.Collections.Generic/SortedSet`1.xml

@@ -1393,7 +1393,7 @@
           <format type="text/markdown"><![CDATA[
 
 ## Remarks
- An empty set is a proper subset of any other collection. Therefore, this method returns `true` if the collection represented by the current <xref:System.Collections.Generic.SortedSet%601> object is empty unless the `other` parameter is also an empty set.
+ An empty set is a subset of any other collection. Therefore, this method returns `true` if the collection represented by the current <xref:System.Collections.Generic.SortedSet%601> object is empty unless the `other` parameter is also an empty set.
 
  This method always returns `false` if <xref:System.Collections.Generic.SortedSet%601.Count%2A> is greater than or equal to the number of elements in `other`.
 
@@ -1462,7 +1462,7 @@
           <format type="text/markdown"><![CDATA[
 
 ## Remarks
- An empty set is a proper superset of any other collection. Therefore, this method returns `true` if the collection represented by the `other` parameter is empty unless the current <xref:System.Collections.Generic.SortedSet%601> collection is also empty.
+ An empty set is a subset of any other collection. Therefore, this method returns `true` if the collection represented by the `other` parameter is empty unless the current <xref:System.Collections.Generic.SortedSet%601> collection is also empty.
 
  This method always returns `false` if <xref:System.Collections.Generic.SortedSet%601.Count%2A> is less than or equal to the number of elements in `other`.
 

xml/System.Collections.Immutable/ImmutableSortedSet`1.xml

@@ -624,7 +624,7 @@ If you need to perform multiple operations on an immutable collection, to increa
           <format type="text/markdown"><![CDATA[
 
 ## Remarks
-An empty set is a proper subset of any other collection. Therefore, this method returns `true` if the current set is empty, unless the `other` collection is also empty.
+An empty set is a subset of any other collection. Therefore, this method returns `true` if the current set is empty, unless the `other` collection is also empty.
 
 [System.Collections.Immutable NuGet package](https://www.nuget.org/packages/System.Collections.Immutable/)
 
@@ -679,7 +679,7 @@ An empty set is a proper subset of any other collection. Therefore, this method
 
 ## Remarks
 
-An empty set is a proper superset of any other collection. Therefore, this method returns `true` if the collection represented by the `other` parameter is empty, unless the current set is also empty.
+An empty set is a subset of any other collection. Therefore, this method returns `true` if the collection represented by the `other` parameter is empty, unless the current set is also empty.
 
 [System.Collections.Immutable NuGet package](https://www.nuget.org/packages/System.Collections.Immutable/)