[NFC] Removing pessimizing move from Support/TaskQueue.h

[ncv]

Summary

No functional change, but allows copy elision to take place.

llvm/include/llvm/Support/TaskQueue.h

std::future<ResultTy> F = T.P->get_future();
       // task immediately.
       if (IsTaskInFlight)
         Tasks.push_back(std::move(T));
       else {
         Scheduler.async(std::move(T));
         IsTaskInFlight = true;
       }
     }
-    return std::move(F);
+    return F;
   }
 
 private:
   void completeTask() {
     // We just completed a task.  If there are no more tasks in the queue,
     // update IsTaskInFlight to false and stop doing work.  Otherwise
     // schedule the next task (while not holding the lock).
     std::function<void()> Continuation;