Fix mistake (?) in IEnumerable<T> documentation. (#3240)

* Fix mistake (?) in IEnumerable<T> documentation.

AFAIS, a reference to the non-generic interface was intended by the original author.

* Update xml/System.Collections.Generic/IEnumerable`1.xml

Co-Authored-By: Ron Petrusha <[email protected]>

* Update xml/System.Collections.Generic/IEnumerable`1.xml

Co-Authored-By: Maira Wenzel <[email protected]>

* Removed extraneous <para> element

Author: m-ringler

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

@@ -63,8 +63,7 @@
  ]]></format>
     </remarks>
     <block subset="none" type="overrides">
-      <para>
-        <see cref="T:System.Collections.Generic.IEnumerable`1" /> is included for parity with non-generic collections; implementing <see cref="T:System.Collections.Generic.IEnumerable`1" /> allows a generic collection to be passed to a method that expects an <see cref="T:System.Collections.IEnumerable" /> object.</para>
+      <para>To remain compatible with methods that iterate non-generic collections, <see cref="T:System.Collections.Generic.IEnumerable`1" /> implements <see cref="T:System.Collections.IEnumerable" />. This allows a generic collection to be passed to a method that expects an <see cref="T:System.Collections.IEnumerable" /> object.</para>
     </block>
     <altmember cref="T:System.Collections.Generic.IEnumerator`1" />
     <altmember cref="N:System.Collections" />