Update OrdinalIgnoreCase to indicate it can't be combined

Author: PranavSenthilnathan

xml/System.Globalization/CompareOptions.xml

@@ -428,7 +428,7 @@
       </ReturnValue>
       <MemberValue>268435456</MemberValue>
       <Docs>
-        <summary>String comparison must ignore case, then perform an ordinal comparison. This technique is equivalent to converting the string to uppercase using the invariant culture and then performing an ordinal comparison on the result.</summary>
+        <summary>String comparison must ignore case, then perform an ordinal comparison. This technique is equivalent to converting the string to uppercase using the invariant culture and then performing an ordinal comparison on the result. This value cannot be combined with other <see cref="T:System.Globalization.CompareOptions" /> values and must be used alone.</summary>
       </Docs>
     </Member>
     <Member MemberName="StringSort">