Release 4.0.0.3

[bgilbert]

openslide-bin release process

• If there's a new OpenSlide release, remove dev_deps condition from any subprojects used by the new release
• Run workflow to check for updates
• Merge any resulting PR; perform any needed manual updates reported by the workflow
• Submit PR to update CHANGELOG.md and _PROJECT_VERSION
• Land PR
• Create and push signed tag
• Find the workflow run for the tag
  • Once the build finishes, approve deployment to PyPI
• Verify that CI creates a PyPI release with a description, source tarball, and wheels
• Verify that CI creates a GitHub release with release notes, software versions, and artifacts
• Update website: _data/releases.yaml, maybe _includes/news.md
• Possibly send mail to -announce and -users
• Possibly post to forum.image.sc

[bgilbert]

The purpose of this release is to drop OpenSlide Java so we're not shipping an old version in the official binaries.

Dependency updates: skipping libffi for this release; gdk-pixbuf update hasn't landed in wrapdb and doesn't contain anything significant.