Bump ipykernel from 6.21.2 to 6.25.2

Bumps [ipykernel](https://github.com/ipython/ipykernel) from 6.21.2 to 6.25.2.
- [Release notes](https://github.com/ipython/ipykernel/releases)
- [Changelog](https://github.com/ipython/ipykernel/blob/main/CHANGELOG.md)
- [Commits](ipython/ipykernel@v6.21.2...v6.25.2)

---
updated-dependencies:
- dependency-name: ipykernel
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

docs/requirements.txt

@@ -1,4 +1,4 @@
-ipykernel==6.21.2
+ipykernel==6.25.2
 nbsphinx==0.9.2
 pydata-sphinx-theme==0.13.3
 sphinx==7.0.1