Bump mhausenblas/mkdocs-deploy-gh-pages from 1.20 to 1.21

Bumps [mhausenblas/mkdocs-deploy-gh-pages](https://github.com/mhausenblas/mkdocs-deploy-gh-pages) from 1.20 to 1.21.
- [Release notes](https://github.com/mhausenblas/mkdocs-deploy-gh-pages/releases)
- [Commits](https://github.com/mhausenblas/mkdocs-deploy-gh-pages/compare/1.20...1.21)

```
updated-dependencies:
- dependency-name: mhausenblas/mkdocs-deploy-gh-pages
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Change-Id: I8f5be517028ffa5c6798e4a6adc223fc8204ed98
1 file changed