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

Author: renovate[bot]

requirements.txt

@@ -12,7 +12,7 @@ mergedeep==1.3.4
 mike==1.1.2
 mkdocs==1.4.2
 mkdocs-git-revision-date-localized-plugin==1.1.0
-mkdocs-material==8.5.11
+mkdocs-material==9.1.21
 mkdocs-material-extensions==1.1.1
 packaging==21.3
 Pygments==2.14.0