`use_amp` is broken in 0.7.0

[rmrao]

I see that use_amp is deprecated but since the Trainer still accepts it as an argument, I believe this is still a bug.

The issue is that the hook that deals with this specifically checks if trainer.precision == 16. However, the Trainer does not set precision = 16 if use_amp = True.

Proposed solution:

if use_amp is passed in, set precision = 16 and raise a deprecation warning.

[Borda]

that s a good catch, thx! could send a fix PR? 🤖

[rmrao]

Submitted!