Bump pytorch-lightning from 1.4.2 to 1.6.0

Bumps [pytorch-lightning](https://github.com/Lightning-AI/lightning) from 1.4.2 to 1.6.0.
- [Release notes](https://github.com/Lightning-AI/lightning/releases)
- [Changelog](https://github.com/Lightning-AI/lightning/blob/1.6.0/CHANGELOG.md)
- [Commits](https://github.com/Lightning-AI/lightning/compare/1.4.2...1.6.0)

---
updated-dependencies:
- dependency-name: pytorch-lightning
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -3,7 +3,7 @@ opencv-python
 pudb==2019.2
 imageio==2.9.0
 imageio-ffmpeg==0.4.2
-pytorch-lightning==1.4.2
+pytorch-lightning==1.6.0
 torchmetrics==0.6
 omegaconf==2.1.1
 test-tube>=0.7.5