Bump pytorch-lightning

Bumps [pytorch-lightning](https://github.com/Lightning-AI/lightning) from 1.0.4 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/1.0.4...1.6.0)

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

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

examples/NLU/examples/research_projects/seq2seq-distillation/requirements.txt

@@ -4,7 +4,7 @@ psutil
 sacrebleu
 rouge-score
 tensorflow_datasets
-pytorch-lightning==1.0.4
+pytorch-lightning==1.6.0
 matplotlib
 git-python==1.0.3
 faiss-cpu