fix: handle multiple gitlab groups (config argument) properly

Why

Before the fix, whenever multiple groups are passed to the config like this:

{
  "api_url": "https://gitlab.com",
  "private_token": "XXXXXX",
  "projects": "",
  "groups": "1234 5678",
  "start_date": "2020-04-01T00:00:00Z"
}

the project-level API requests fetch only project data for the first group: 1234, completely skipping projects of group 5678.

The reason is that this condition https://gitlab.com/meltano/tap-gitlab/-/blob/master/tap_gitlab/init.py#L477 is never met for the 2nd, 3rd, 4th etc group - because pids of the 1st group are already occupying the list.

What

Move sync_project execution inside the "if" statement which checks whether any pids have been provided to the tap. If no pids were provided, just execute sync_project on the fly but don't persist "pids of a group" so that the 2nd, 3rd and next iterations of the for gid in gids loop are not impacted.