build(deps): bump pytorch-lightning from 1.9.5 to 2.6.0 in /tests/e2e

Bumps [pytorch-lightning](https://github.com/Lightning-AI/lightning) from 1.9.5 to 2.6.0.
- [Release notes](https://github.com/Lightning-AI/lightning/releases)
- [Commits](Lightning-AI/pytorch-lightning@1.9.5...2.6.0)

---
updated-dependencies:
- dependency-name: pytorch-lightning
  dependency-version: 2.6.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

tests/e2e/mnist_pip_requirements.txt

@@ -1,6 +1,6 @@
 --extra-index-url https://download.pytorch.org/whl/cu118
 torch==2.7.1+cu118
 torchvision==0.22.1+cu118
-pytorch_lightning==1.9.5
+pytorch_lightning==2.6.0
 torchmetrics==1.8.2
 minio