Fix two pessimizing moves.

See https://en.cppreference.com/w/cpp/language/return#Automatic_move_from_local_variables_and_parameters

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D94218

llvm/include/llvm/Support/TaskQueue.h

@@ -98,7 +98,7 @@ public:
         IsTaskInFlight = true;
       }
     }
-    return std::move(F);
+    return F;
   }
 
 private:

mlir/include/mlir/Parser.h

@@ -67,7 +67,7 @@ inline OwningOpRef<ContainerOpT> constructContainerOpForParserIfNecessary(
   // contain the operations inside of it.
   if (failed(op.verify()))
     return OwningOpRef<ContainerOpT>();
-  return std::move(opRef);
+  return opRef;
 }
 } // end namespace detail