cython
sphinx < 2.0
sphinx_rtd_theme
sphinx-gallery
sphinxcontrib-apidoc
pillow
pytest
pytest-cov
pylint
sympy
wheel
twine
vtk
pyvista>=0.20.1
numpydoc
nbsphinx
coverage
codecov
omf
matplotlib
pymatsolver>=0.1.2

cython
sphinx
sphinx_rtd_theme
sphinx-gallery
sphinxcontrib-apidoc
pillow
pytest
pytest-cov
pylint
sympy
wheel
twine
vtk
pyvista>=0.20.1
numpydoc
nbsphinx
coverage
codecov
omf
matplotlib
pymatsolver>=0.1.2

Remove restriction of sphinx < 2
Remove restriction of sphinx < 2

- The upcoming sphinx_rtd_theme v0.5.0 has a fix for the issue why we
  pinned it originally.
- numpydoc v1.0.0 was released, what also helps.
- sphinx is alread at version > 3, which I think is not that affected
  either.

Maybe wait with merging until v0.5.0 of sphinx_rtd_theme is out:
ttps://pypi.org/project/sphinx-rtd-theme
