[clang] [clang-tools-extra] Remove `StringLiteral` in favor of `StringRef` (PR #122366)

[Benoit Jacob via cfe-commits]

================
@@ -57,7 +57,7 @@ class DeclarationFragments {
     Keyword,
     Attribute,
     NumberLiteral,
-    StringLiteral,
+    StringRef,
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bjacob wrote:

good catch! i'll pore over the actual diff line by line to catch more things like this, but I wanted to first see if this PR would be shot down at a higher level :-)

https://github.com/llvm/llvm-project/pull/122366