The previous job always used the last release version of
releaser-pleaser. This caused two issues:
- if new flags were added to `action.yml` since the last release, the
program errored because the flags are unknown.
- right after merging a release pr, the image reference was already
updated, but no new container image was built yet.
This fixes both issues, by using a locally built version of
releaser-pleaser, which is always up-to-date and available.
