Bump mkdocs-material from 9.6.20 to 9.6.21 in /docs in the docs group (#881)

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

@@ -1,7 +1,7 @@
 mkdocs-callouts>=1.13.2
 mkdocs-git-authors-plugin>=0.8.0
 mkdocs-git-revision-date-localized-plugin>=1.2.5
-mkdocs-material==9.6.20
+mkdocs-material==9.6.21
 mkdocs-table-reader-plugin>=2.1.0
 mkdocs==1.6.1
 pandas>=2.0.3