clean up (dotnet#4675)

Author: gewarren

xml/System.Runtime.CompilerServices/MethodImplOptions.xml

@@ -51,7 +51,7 @@
     </Attribute>
   </Attributes>
   <Docs>
-    <summary>Defines the details of how a method is implemented.</summary>
+    <summary>Specifies constants that define the details of how a method is implemented.</summary>
     <remarks>
       <format type="text/markdown"><![CDATA[  
   
@@ -61,7 +61,7 @@
  You can specify multiple <xref:System.Runtime.CompilerServices.MethodImplOptions> values by using the bitwise OR operator.  
   
 > [!NOTE]
->  Locking on the instance or on the type, as with the Synchronized flag, is not recommended for public types, because code other than your own can take locks on public types and instances. This might cause deadlocks or other synchronization problems.  
+> Locking on the instance or on the type, as with the `Synchronized` flag, is not recommended for public types, because code other than your own can take locks on public types and instances. This might cause deadlocks or other synchronization problems.  
   
  ]]></format>
     </remarks>
@@ -205,7 +205,7 @@
       </ReturnValue>
       <MemberValue>4096</MemberValue>
       <Docs>
-        <summary>The call is internal, that is, it calls a method that is implemented within the common language runtime.</summary>
+        <summary>The call is internal, that is, it calls a method that's implemented within the common language runtime.</summary>
       </Docs>
     </Member>
     <Member MemberName="NoInlining">