Merge pull request #280 from backstage/renovate/mkdocs-material-9.x

chore(deps): update dependency mkdocs-material to v9.6.15

Author: awanlin

requirements.txt

@@ -9,7 +9,7 @@ Markdown>=3.2,<3.9
 # pinned to an exact version. Bumps should be accompanied by release notes
 # explaining what was added or fixed (or at least pointing to the underlying
 # release notes of the bumped package).
-mkdocs-material==9.6.14
+mkdocs-material==9.6.15
 markdown-graphviz-inline==1.1.3
 mkdocs-monorepo-plugin==1.1.2
 plantuml-markdown==3.11.1