Bump sphinx from 3.5.2 to 3.5.3 in /docs

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.5.2 to 3.5.3.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/3.x/CHANGES)
- [Commits](https://github.com/sphinx-doc/sphinx/commits)

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

Author: dependabot-preview[bot]

docs/requirements.txt

@@ -1,7 +1,7 @@
 # This file is used to setup env
 # to generate documentation.
 
-sphinx==3.5.2
+sphinx==3.5.3
 sphinx_autodoc_typehints==1.11.1
 sphinxcontrib-mermaid==0.6.3
 sphinx-typlog-theme==0.8.0