Bump sphinx-autobuild from 2020.9.1 to 2021.3.14

Bumps [sphinx-autobuild](https://github.com/executablebooks/sphinx-autobuild) from 2020.9.1 to 2021.3.14.
- [Release notes](https://github.com/executablebooks/sphinx-autobuild/releases)
- [Changelog](https://github.com/executablebooks/sphinx-autobuild/blob/main/NEWS.rst)
- [Commits](https://github.com/executablebooks/sphinx-autobuild/commits)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

requirements.txt

@@ -4,7 +4,7 @@ sphinx==3.5.2
 sphinx-tabs==2.1.0
 sphinxemoji==0.1.8
 sphinx-rtd-theme==0.5.1
-sphinx-autobuild==2020.9.1
+sphinx-autobuild==2021.3.14
 pylama==7.7.1
 requests==2.25.1
 jinja2==2.11.3