Revert "[clang-format][NFC] Remove a redundant isLiteral() call"

This reverts commit f603369.
This change is labeled as NFC, but introduces a functional change
without a test, and caused a breakage as reported in
https://reviews.llvm.org/rGf6033699646b7650123a273c043a93e5eeaac6d8.

Author: gulfemsavrun

clang/lib/Format/TokenAnnotator.cpp

@@ -3409,8 +3409,10 @@ static bool isFunctionDeclarationName(bool IsCpp, const FormatToken &Current,
         Tok->isOneOf(TT_PointerOrReference, TT_StartOfName, tok::ellipsis)) {
       return true;
     }
-    if (Tok->isOneOf(tok::l_brace, TT_ObjCMethodExpr) || Tok->Tok.isLiteral())
+    if (Tok->isOneOf(tok::l_brace, tok::string_literal, TT_ObjCMethodExpr) ||
+        Tok->Tok.isLiteral()) {
       return false;
+    }
   }
   return false;
 }