python3-sphinx-rtd-theme: upgrade 2.0.0 -> 3.0.0

python3-sphinx-rtd-theme: upgrade 2.0.0 -> 3.0.0

Changelog:
===========
- Trigger search modal on "Search docs" input focus
- Show hidden version in selector if it's the current active version
- Show version/language selectors below the title
- Docs: do not sign Git tag
- Docs: update the installation note
- Theme option flyout to enable/disable theme's flyout
- Populate html_context with READTHEDOCS_* environment variables
- Tests: sphinxdev tox environment installs Sphinx from master
- Docs: update releasing
- Adjust the expected test_basic output to match Sphinx 7.3+
- Addons: integrate with new beta addons flyout
- Remove html5shiv
- Remove Sphinx<5 compatibility leftovers
- Remove pytest warnings

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>