Release Pillow 10.4.0 on July 1, 2024

Main Release

Released quarterly on January 2nd, April 1st, July 1st and October 15th.

[x] Open a release ticket e.g. https://github.com/python-pillow/Pillow/issues/3154
[x] Develop and prepare release in main branch.
[x] Check GitHub Actions and AppVeyor to confirm passing tests in main branch.
[x] Check that all the wheel builds pass the tests in the GitHub Actions "Wheels" workflow jobs by manually triggering them.
[x] In compliance with PEP 440, update version identifier in src/PIL/_version.py
[x] Update CHANGES.rst.
[x] Run pre-release check via make release-test in a freshly cloned repo.

[x] Create branch and tag for release e.g.:

git branch 10.4.x
git tag 10.4.0
git push --tags

[x] Check the GitHub Actions "Wheels" workflow has passed, including the "Upload release to PyPI" job. This will have been triggered by the new tag.
[x] Publish the release on GitHub.
[x] In compliance with PEP 440, increment and append .dev0 to version identifier in src/PIL/_version.py and then:
```
git push --all
```
Publicize Release
[x] Announce release availability via Mastodon e.g. https://fosstodon.org/@pillow/110639450470725321

[x] Make sure the default version for Read the Docs is up-to-date with the release changes

[x] Update Pillow in the Docker Images repository

git clone https://github.com/python-pillow/docker-images
cd docker-images
./update-pillow-tag.sh [[release tag]]