[future] Minor: std::move() callback in future for the convenience operator case. (#37861)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37861
ghstack-source-id: 103511066
Test Plan: buck test mode/dev-nosan caffe2/test/...
Differential Revision: D21409650
fbshipit-source-id: 6c501963f73590512e426f6806f4530aad618b1a