build(deps): update pytorch-lightning requirement in /_requirements

Updates the requirements on [pytorch-lightning](https://github.com/Lightning-AI/lightning) to permit the latest version.
- [Release notes](https://github.com/Lightning-AI/lightning/releases)
- [Commits](Lightning-AI/pytorch-lightning@1.4.0...2.2.0.post0)

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

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

_requirements/default.txt

@@ -3,5 +3,5 @@ matplotlib>=3.0.0, <3.9.0
 ipython[notebook]>=8.0.0, <8.17.0
 urllib3  # for ipython
 torch>=1.8.1, <2.1.0
-pytorch-lightning>=1.4, <2.1.0
+pytorch-lightning>=1.4, <2.3.0
 torchmetrics>=0.7, <1.3