This pin means that sites will not show an update available for docker_manager, and will then hit a pnpm/yarn error when updating core.
docker_manager is compatible with the 3.3.x series, so we can remove this pin.
This introduces a fallback compatibility parser, identical to the one introduced in https://github.com/discourse/discourse/pull/22714
This will allow Docker Manager to parse new compatibility files, even when running on older Discourse instances. This is only intended as a temporary solution, and will be removed before the Discourse 3.2 release.
Without this upgrades to v3.1.0.beta4+ will fail because those newer versions require Ruby 3.2 and the old, pinned docker_manager version didn't prompt for a CLI rebuild when upgrading from v3.1.0.beta1 and below.
The actual fix is in 1b2d7eb which is part of the new `old-version-up-to-v3.1.0.beta1` branch.