Fix "the currently item" (dotnet#1625)

Author: jnm2

xml/System.Collections.Immutable/ImmutableArray`1+Enumerator.xml

@@ -45,7 +45,7 @@
         <ReturnType>T</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>Gets the currently item.</summary>
+        <summary>Gets the current item.</summary>
         <value>The current item.</value>
         <remarks>To be added.</remarks>
       </Docs>
@@ -77,4 +77,4 @@
       </Docs>
     </Member>
   </Members>
-</Type>
+</Type>