build(deps): bump mkdocs-material from 8.2.14 to 8.2.15 in /docs (#898)

Bumps [mkdocs-material](https://github.com/squidfunk/mkdocs-material) from 8.2.14 to 8.2.15.
- [Release notes](https://github.com/squidfunk/mkdocs-material/releases)
- [Changelog](https://github.com/squidfunk/mkdocs-material/blob/master/CHANGELOG)
- [Commits](squidfunk/mkdocs-material@8.2.14...8.2.15)

---
updated-dependencies:
- dependency-name: mkdocs-material
  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]

docs/requirements.txt

@@ -1,3 +1,3 @@
 mike==1.1.2
-mkdocs-material==8.2.14
+mkdocs-material==8.2.15
 mkdocs-git-revision-date-plugin==0.3.2