[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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@@ -119,23 +118,16 @@ void UseIntegerSignComparisonCheck::check(
   Expr::EvalResult EVResult;
   if (!SignedCastExpression->isValueDependent() &&
       SignedCastExpression->getSubExpr()->EvaluateAsInt(EVResult,
-                                                        *Result.Context)) {
-    const llvm::APSInt SValue = EVResult.Val.getInt();
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localspook wrote:

`getInt()` returns a reference, so this is an unnecessary copy

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