Bump sphinx-rtd-theme from 0.5.0 to 2.0.0

Bumps [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) from 0.5.0 to 2.0.0.
- [Changelog](https://github.com/readthedocs/sphinx_rtd_theme/blob/master/docs/changelog.rst)
- [Commits](readthedocs/sphinx_rtd_theme@0.5.0...2.0.0)

---
updated-dependencies:
- dependency-name: sphinx-rtd-theme
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

setup.cfg

@@ -87,7 +87,7 @@ dev =
     sphinxcontrib-napoleon~=0.7
     tox~=3.28.0
     flask_testing~=0.8.0
-    sphinx-rtd-theme~=0.5.0
+    sphinx-rtd-theme>=0.5,<2.1
     sphinx-argparse~=0.2.5
     behave~=1.2.6
     allure-behave~=2.8.13