A-S nightly bumps don't seem to the major version into account

[rvandermeulen]

This week after the start of the new Nightly 116 cycle, we forgot to bump the major version in the AppServices repo, so Nightly builds were still being produced as 115.YYYYMMDD format. However, relbot was still dutifully creating update PRs for firefox-android main even though it was bumped to 116 on the main branch. While this didn't really cause any damage in practice, we probably should have a safeguard there just in case.