gitlab: increase Cirrus CI timeout to 90 minutes

The current FreeBSD task is sometimes timing out on the Cirrus CI
task, which is limited to 60 minutes by default. Increasing it to
90 minutes gives us significantly more headroom, even though we
hope it won't take that long normally.

On the GitLab side we're invoking the Cirrus CI job using the
cirrus-run tool which speaks to the Cirrus REST API. Cirrus
sometimes tasks 5-10 minutes to actually schedule the task,
and thus the execution time of 'cirrus-run' inside GitLab will
be slightly longer than the execution time of the Cirrus CI
task. The GitLab job timeout is set to have 10 minutes extra
grace, so that ideally we timeout on the Cirrus CI side before
GitLab CI timeouts can hit.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>