[clang-tools-extra] [clang-tidy][NFC] Clean up and slightly optimize `modernize-use-integer-sign-comparison` (PR #163492)

[Victor Chernyakin via cfe-commits]

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@@ -34,13 +34,12 @@ AST_MATCHER(clang::QualType, isActualChar) {
 } // namespace
 
 static BindableMatcher<clang::Stmt>
-intCastExpression(bool IsSigned,
-                  const std::string &CastBindName = std::string()) {
+intCastExpression(bool IsSigned, StringRef CastBindName = {}) {
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localspook wrote:

`StringRef` is enough here, we don't need `std::string`

https://github.com/llvm/llvm-project/pull/163492