Basic: tweak whitespace in Attr.td

Separate two class definitions that had been merged into a single line.  NFC.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@239878 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/Attr.td

@@ -195,7 +195,8 @@ class CXX11<string namespace, string name, int version = 1>
     : Spelling<name, "CXX11"> {
   string Namespace = namespace;
   int Version = version;
-} class Keyword<string name> : Spelling<name, "Keyword">;
+}
+class Keyword<string name> : Spelling<name, "Keyword">;
 class Pragma<string namespace, string name> : Spelling<name, "Pragma"> {
   string Namespace = namespace;
 }