build(deps): bump plexapi from 4.15.3 to 4.15.4

Bumps [plexapi](https://github.com/pkkid/python-plexapi) from 4.15.3 to 4.15.4.
- [Release notes](https://github.com/pkkid/python-plexapi/releases)
- [Commits](pkkid/python-plexapi@4.15.3...4.15.4)

---
updated-dependencies:
- dependency-name: plexapi
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>