Bump sphinx-notfound-page from 0.6 to 0.7.1
Bumps [sphinx-notfound-page](https://github.com/readthedocs/sphinx-notfound-page) from 0.6 to 0.7.1.
- [Release notes](https://github.com/readthedocs/sphinx-notfound-page/releases)
- [Changelog](https://github.com/readthedocs/sphinx-notfound-page/blob/0.7.1/CHANGELOG.rst)
- [Commits](https://github.com/readthedocs/sphinx-notfound-page/compare/0.6...0.7.1)
Signed-off-by: dependabot[bot] <[email protected]>
(cherry picked from commit 7f2a3e8b55fd38e8e7fef4e9b37becc6cd1f3f4e)