Fix grammar.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@255727 91177308-0d34-0410-b5e6-96231b3b80d8

www/comparison.html

@@ -100,7 +100,8 @@
         for <a href="diagnostics.html">expressive diagnostics</a>.
         Modern versions of GCC have made significant advances in this area,
         incorporating various Clang features such as preserving typedefs in
-        diagnostics and showing macro expansions, but is still catching up.</li>
+        diagnostics and showing macro expansions, but GCC is still catching
+        up.</li>
     <li>GCC is licensed under the GPL license. <a href="features.html#license">
         clang uses a BSD license,</a> which allows it to be embedded in
         software that is not GPL-licensed.</li>