Update ImmutableDictionary`2.xml

Author: WhiteBlackGoose

xml/System.Collections.Immutable/ImmutableDictionary`2.xml

@@ -97,7 +97,7 @@
       <format type="text/markdown"><![CDATA[
 
 ## Remarks
-  When you manipulate an immutable dictionary, a new one is returned with the appropriate changes, while the old one is not altered.
+ When you manipulate an immutable dictionary, a new one is returned with the appropriate changes, while the old one is not altered.
 
 ## Examples
 This example shows how to create an immutable dictionary and get values from it: