Revert "Gate jeepyb and openstack/requirements on pbr"

This reverts commit 8a76bf3788f80302250296e8e999b3c2912bc5fd.

The parentheses workaround for the JJB parsing bug mentioned in the
review notes turned out to not actually function in the resulting
job.

Change-Id: I10e2f6164e616fbaaabbfc3328c6f4bd620d5621
Merge "Revert "Gate jeepyb and openstack/requirements on pbr""