Simplify release process. (#112)

Author: JulienPalard

CONTRIBUTING.rst

@@ -10,9 +10,8 @@
   ``./venv/bin/pip install ../../python-docs-theme/dist/python-docs-theme-2021.8.tar.gz``
   then build the doc using ``make html``).
 - upload it: ``twine upload dist/*``.
-- bump version (YYYY.MM.dev) in setup.py and python_docs_theme/theme.conf
-- Commit this last bump.
-- push and push the tag (``git push && git push --tags``)
+- push the tag (``git push --tags``)
+
 
 # Makefile usage