Delete obsolete `4-snapshot` and `4-snapshot-trixie` tags from Docker Hub

[fdcastel]

@asfernandes — could you delete two tags from firebirdsql/firebird on Docker Hub when you have a moment? I don't have credentials for the registry.

Tags to delete:

• firebirdsql/firebird:4-snapshot
• firebirdsql/firebird:4-snapshot-trixie

Background

While verifying the publish run after merging #36, I dispatched the snapshot workflow for all three branches (master, v5.0-release, v4.0) to refresh the snapshot tags. The v4.0 dispatch unintentionally pushed 4-snapshot tags, which:

• aren't advertised in the README (only 6-snapshot and 5-snapshot are documented), and
• are amd64-only — Firebird 4.x has no linux-arm64 snapshot tarball in FirebirdSQL/snapshots, same root cause as D-015.

The snapshot workflow has since been fixed (see f63bf31) to exclude v4.0/arm64 from the matrix, and master / v5.0-release snapshots have been re-published as proper multi-arch manifests. The 4-snapshot* tags are the only leftover.

Quickest path: Docker Hub UI → https://hub.docker.com/r/firebirdsql/firebird/tags → tick the two tags → delete.

Thanks!

[asfernandes]

Done.