[clang] [StaticAnalyzer] Drop const from a return type (NFC) (PR #141414)

[Matt Arsenault via cfe-commits]

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@@ -537,7 +537,7 @@ class StdLibraryFunctionsChecker
     /// a later bug report created by ErrnoChecker.
     /// Empty return value means that 'errno' related bug may not happen from
     /// the current analyzed function.
-    virtual const std::string describe(CheckerContext &C) const { return ""; }
+    virtual std::string describe(CheckerContext &C) const { return ""; }
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arsenm wrote:

Can this return StringRef? 

https://github.com/llvm/llvm-project/pull/141414