PM: silence `-Wpessimizing-move` from GCC 9.2.1 (NFC)

Remove the explicit move enabling NVRO.
diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
index 1aaccb5..5c4874d 100644
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -1445,7 +1445,7 @@
   Expected<ParametersT> Result = Parser(Params);
   assert((Result || Result.template errorIsA<StringError>()) &&
          "Pass parameter parser can only return StringErrors.");
-  return std::move(Result);
+  return Result;
 }
 
 /// Parser of parameters for LoopUnroll pass.