[interim fix] of sphinx-tabs and sphinx-jinja

The myst-parser requires >= docutils v.0.17 what ends in a dependency hell where
plugins sphinx-tabs and sphinx-jinja we use are involved.

This patch can be reverted when [2], [3], [4]  are solved and new release is
available / see [1].

[1] https://github.com/searxng/searxng/pull/954
[2] https://github.com/executablebooks/sphinx-tabs/issues/152
[3] https://github.com/executablebooks/sphinx-tabs/pull/153
[4] https://github.com/executablebooks/sphinx-tabs/pull/154



Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>