Fix typo and avoid layout issue with almost-but-not-quite-fixed-width fonts.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156095 91177308-0d34-0410-b5e6-96231b3b80d8

docs/LanguageExtensions.html

@@ -1544,8 +1544,7 @@ case 55:  // no warning
   }
 case 66:  // no warning
   p();
-  <b>[[clang::fallthrough]];</b>  // warning: fallthrough annotation does not directly
-                           //          preceed case label
+  <b>[[clang::fallthrough]];</b>  // warning: fallthrough annotation does not directly precede case label
   q();
 case 77:  // warning: unannotated fall-through
   r();