[ObjCopy] Use StringRef::starts_with (NFC)#139408

kazutakahirata merged 1 commit intollvm:mainllvm/llvm-project:mainfrom

kazutakahirata:cleanup_001_StringRef_starts_with_llvm_ObjCopykazutakahirata/llvm-project:cleanup_001_StringRef_starts_with_llvm_ObjCopyCopy head branch name to clipboard