Added EII boilerplate to GroupCollection member (#2836)

Author: Ron Petrusha

xml/System.Text.RegularExpressions/GroupCollection.xml

@@ -1064,7 +1064,15 @@ This member is an explicit interface member implementation. It can be used only
         <param name="array">The one-dimensional array the collection is to be copied into.</param>
         <param name="arrayIndex">The zero-based index in the destination array where copying is to begin.</param>
         <summary>Copies all the elements of the collection to the specified array beginning at the specified index.</summary>
-        <remarks>To be added.</remarks>
+        <remarks>  
+          <format type="text/markdown"><![CDATA[  
+
+## Remarks
+
+This member is an explicit interface member implementation. It can be used only when the <xref:System.Text.RegularExpressions.GroupCollection> instance is cast to an <xref:System.Collections.ICollection> interface. 
+
+         ]]></format>
+         </remarks>
         <exception cref="T:System.ArgumentNullException">
           <paramref name="array" /> is null.</exception>
         <exception cref="T:System.IndexOutOfRangeException">