jobs/master-builds.yml: add missing job type 'distcheck'
We do have this job type in gerrit-verifications.yml, so it's executed for each patch submitted to Gerrit. However, we are not executing 'distcheck' during the daily master builds - fix this.
Change-Id: I4898ba712a29a6afc34bc22adec6a3131ce8c794 Fixes: 31fd5cf0 ("gerrit-verifications: execute 'distcheck' job for pysim")
