Update dependency mkdocs-material to v9.6.20 (#93)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

requirements-docs.txt

@@ -1,3 +1,3 @@
-mkdocs-material==9.6.19
+mkdocs-material==9.6.20
 mkdocs-table-reader-plugin==2.2.2
 mkdocs-git-revision-date-localized-plugin