v0.13.3b1 and v0.13.3b2 drafted after v0.14.0b1

[ErikBjare]

See https://github.com/ActivityWatch/activitywatch/releases/tag/untagged-a737870ed430b493ffb1 which was drafted after https://github.com/ActivityWatch/activitywatch/releases/tag/v0.14.0b1 probably by the scheduled release CI job.

A proper such draft release would be v0.14.0b2, not create beta releases for the next patch when a beta for a new minor exists.

@TimeToBuildBob Get on it

[TimeToBuildBob]

Fix in #1308.

Root cause: the workflow computed next_base by bumping latest_stable (v0.13.2) by the RELEASE_LINE (patch → v0.13.3), then only searched for v0.13.3bN tags. It never checked whether a prerelease for a newer version (v0.14.0b1) already existed.

The fix adds a check after computing next_base: find the highest existing prerelease tag across all versions, and if it's newer than next_base, continue that release line instead.

Also worth deleting the stale v0.13.3b1 / v0.13.3b2 draft releases.

[ErikBjare]

Also, both those releases have 0 commits diff from v0.14.0b1, so shouldn't have been drafted at all.