Fix GPG key deletion during account deletion (#14561) (#14569)

Fix GPG key deletion during account deletion (#14561) (#14569)

Per #14531, deleting a user account will delete the user's GPG keys
from the `gpg_key` table but not from `gpg_key_import`, which causes
an error when creating an account with the same email and attempting
to re-add the same key. This commit deletes all entries from
`gpg_key_import` that match any GPG key IDs belonging to the user.

Co-authored-by: Anton Khimich <anton.khimicha@mail.utoronto.ca>