deprecate metrics pkg (#6505)

* deprecate metrics

* examples

* req

* docs

* Apply suggestions from code review

Co-authored-by: Carlos Mocholí <[email protected]>
Co-authored-by: Nicki Skafte <[email protected]>

* pep8

Co-authored-by: Carlos Mocholí <[email protected]>
Co-authored-by: Nicki Skafte <[email protected]>

Author: 3 people

CHANGELOG.md

@@ -65,6 +65,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Deprecated `trainer.running_sanity_check` in favor of `trainer.sanity_checking` ([#4945](https://github.com/PyTorchLightning/pytorch-lightning/pull/4945))
 
 
+- Deprecated metrics in favor of `torchmetrics` ([#6505](https://github.com/PyTorchLightning/pytorch-lightning/pull/6505))
+
+
 ### Removed
 
 - Removed support for passing a bool value to `profiler` argument of Trainer ([#6164](https://github.com/PyTorchLightning/pytorch-lightning/pull/6164))