Update pyproject.toml

[wouterdb]

Add jinja 4 support to sphinx-tabs

should fix inmanta/inmanta-core#4512

for some reason depdenabot doesn't want to make the bump

Part 2

blocked by readthedocs/sphinx_rtd_theme#1302

  Because sphinx-tabs (3.4.1) depends on docutils (>=0.18.0,<0.19.0)
   and sphinx-rtd-theme (1.0.0) depends on docutils (<0.18), sphinx-tabs (3.4.1) is incompatible with sphinx-rtd-theme (1.0.0).
  So, because inmanta-dev-dependencies depends on both sphinx-rtd-theme (1.0.0) and sphinx-tabs (3.4.1), version solving failed.

[wouterdb]

This can not currently work