ci: do not trigger phabricator for merge-request...
ci: do not trigger phabricator for merge-request
The fast the phabricator steps has a `rules` entry makes it selected for the
special `merge_requests` pipelines. The other ones behave as default and are not
selected tot the mrege_request pipelines.
This result in a second pipeline to be created, with only the phabricator
pipeline in it. Which usually succeed fast (since there is nothing to do).
This is harmful as this create a false sense of "the series is passing" and
Gitlab will use this simplistic pipeline for validation.
By explicitly preventing the pipeline to be created in the merge-request case,
we prevent this situation to happens
Note that the job will be dropped (alonside phabricator) in the next two weeks
anyway.
