build(deps): update torchmetrics requirement

Updates the requirements on [torchmetrics](https://github.com/Lightning-AI/torchmetrics) to permit the latest version.
- [Release notes](https://github.com/Lightning-AI/torchmetrics/releases)
- [Changelog](https://github.com/Lightning-AI/torchmetrics/blob/master/CHANGELOG.md)
- [Commits](Lightning-AI/torchmetrics@v0.8.0...v1.6.0)

---
updated-dependencies:
- dependency-name: torchmetrics
  dependency-type: direct:production
...

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

requirements/_test.txt

@@ -4,4 +4,4 @@ pytest-cov
 pytest-forked ==1.6.0
 
 scikit-learn >0.22.1, <1.6.0
-torchmetrics >=0.8.0, <1.5.0
+torchmetrics >=0.8.0, <1.7.0