R1:ba2ee3a66e89

Make "bin/config set --database ..." resurrect deleted values

Summary:
Fixes T12409. Config entries may be marked as "deleted", and `bin/config set --database` doesn't un-delete them, so the edit doesn't do anything.

The "most correct" fix here is to swap to transactions so we run the same code, but just fix this narrowly for now since it's one line of code.

Test Plan:
- Set `maniphest.default-priority` to `123`.
- Deleted `maniphest.default-priority` from the web UI by deleting all the text in the…