Some database schemas have `members.created_at` set as `timestamp with
time zone`, while on GitLab.com and dev we have `timestamp without time
zone`. If the column has a time zone, the `OrphanedInviteTokensCleanup`
migration fails with the following error:

```
PG::InvalidObjectDefinition: ERROR: functions in index predicate must be
marked IMMUTABLE
```

As described in https://stackoverflow.com/a/58848792, if the time zone
depends on the server, the result might change if somebody changes the
time zone. We need to lock the time zone if the timezone depends on the
server.

We need to make sure the comparison between `created_at` and
`invite_accepted_at` are done using the same types or PostgreSQL will
reject the query due to immutability concerns. Calling `TIMEZONE('UTC',
column)` on a `timestamp without time zone` converts it to `timestamp
with time zone` type. Calling the same function on a `timestamp with
time zone` converts it to a type of `timestamp without time
zone`. Therefore, we should check the type before we do this conversion.

There is an epic that deals with reconciling these datetime with
timezone differences: https://gitlab.com/groups/gitlab-org/-/epics/2473

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/339091

Changelog: fixed