[ByteCode] Drop const from a return type (NFC) (#141415)

Author: kazutakahirata

clang/lib/AST/ByteCode/Function.h

@@ -115,7 +115,7 @@ class Function final {
 
   /// Returns the name of the function decl this code
   /// was generated for.
-  const std::string getName() const {
+  std::string getName() const {
     if (!Source || !getDecl())
       return "<<expr>>";