Bump pytorch-lightning from 1.5.8 to 1.5.9 (ray-project#120)

Bumps [pytorch-lightning](https://github.com/PyTorchLightning/pytorch-lightning) from 1.5.8 to 1.5.9.
- [Release notes](https://github.com/PyTorchLightning/pytorch-lightning/releases)
- [Changelog](https://github.com/PyTorchLightning/pytorch-lightning/blob/1.5.9/CHANGELOG.md)
- [Commits](Lightning-AI/pytorch-lightning@1.5.8...1.5.9)

---
updated-dependencies:
- dependency-name: pytorch-lightning
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements-test.txt

@@ -4,7 +4,7 @@ flake8-comprehensions
 flake8-quotes
 yapf==0.23.0
 pytest
-pytorch-lightning==1.5.8
+pytorch-lightning==1.5.9
 lightning-bolts==0.3.3
 ray[tune]
 torch==1.8.1