Fix incorrect remarks for Nullable<T>.Implicit operator (#2711)

* Fix incorrect remarks for Nullable<T>.Implicit operator

The implicit operator's value parameter is of type T (not T?) and will never be null.

* Note that C# and VB don't use the implicit Nullable operator

Author: MichaelJLiu

xml/System/Nullable`1.xml

@@ -536,11 +536,17 @@
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- If the `value` parameter is not `null`, the <xref:System.Nullable%601.Value%2A> property of the new <xref:System.Nullable%601> value is initialized to the `value` parameter and the <xref:System.Nullable%601.HasValue%2A> property is initialized to `true`.  
-  
- If the `value` parameter is `null`, the <xref:System.Nullable%601.Value%2A> property of the new <xref:System.Nullable%601> value is initialized to the default value, which is the value that is all binary zeroes, and the <xref:System.Nullable%601.HasValue%2A> property is initialized to `false`.  
-  
- The equivalent method for this operator is <xref:System.Nullable%601.%23ctor%28%600%29?displayProperty=nameWithType>]]></format>
+ The <xref:System.Nullable%601.Value%2A> property of the new <xref:System.Nullable%601> value is initialized to the `value` parameter and the <xref:System.Nullable%601.HasValue%2A> property is initialized to `true`.  
+  
+ The equivalent method for this operator is <xref:System.Nullable%601.%23ctor%28%600%29?displayProperty=nameWithType>
+
+> [!NOTE]
+>  In C# and Visual Basic, an implicit conversion from `T` to <xref:System.Nullable%601> does not invoke this operator because these languages have special rules for the conversion. This operator is provided for the benefit of languages that do not have such special rules.
+
+> [!NOTE]
+>  In C# and Visual Basic, an implicit conversion from a `null` or `Nothing` literal to <xref:System.Nullable%601> produces a <xref:System.Nullable%601> value whose <xref:System.Nullable%601.HasValue%2A> property is initialized to `false`. The conversion occurs at compile time in these languages and does not invoke any operator.
+
+]]></format>
         </remarks>
       </Docs>
     </Member>