HACK: Skip OBS scanning by default

The OBS 2.10 update made things sensibly slower, causing timeouts in the
packaging-data-fetch-obs job. Disable it for now.

Set `SKIP_OBS` to `no` to run the job again.

See https://phabricator.apertis.org/T8880



Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>