Update Span`1.xml (#5086)

* Update Span`1.xml

typo and may be better sentence

* Update xml/System/Span`1.xml

awesome, looks perfect.

Co-authored-by: Carlos Sanchez <[email protected]>

Co-authored-by: Carlos Sanchez <[email protected]>

Author: marafiq

xml/System/Span`1.xml

@@ -980,7 +980,7 @@ Two <xref:System.Span%601> objects are equal if they have different lengths or i
         <remarks>
           <format type="text/markdown"><![CDATA[  
 
-This method performs a heap allocation and therefore should be avoided if possible. It it sometimes necessary when APIs that support <xref:System.Span%601> objects are not available but APIs that work with arrays are.
+This method performs a heap allocation and therefore should be avoided if possible. Heap allocations are expected in APIs that work with arrays. Using such APIs is unavoidable if an alternative API overload that takes a <xref:System.Span%601> does not exist.
 
          ]]></format>
         </remarks>