Fix GETEX db delete call to emit DB_FLAG_KEY_EXPIRED on expiration

[enjoy-binbin]

We should emit DB_FLAG_KEY_EXPIRED instead of DB_FLAG_KEY_DELETED.
This is an overlook in #9406.

[oranagra]

should we mention this in the release notes? (considering it's a minor bug that only exists in a pre-release and will be solved in the GA)

[enjoy-binbin]

well. It is a minor bug, so i guess we can skip the release note. But on the other hand, there is no harm mention it in the release notes, i prefer to add it to releade notes

[oranagra]

had that bug existed in an actual release, then i'd probably want to mention it.
but beside being minor, and besides the fact it exists in a module API that i doubt is actually being used by anyone, it also only exists in a pre-release.
so in the rare chance that someone is actually affected, they'll probably upgrade anyway (even without being alerted by the release notes).
on the other hand, if that fix could have had some adverse effect, then they should know before upgrading, but i don't think that's the case.