CI: Drop unneeded CI jobs

CI: Drop unneeded CI jobs

The move to using JCasC to configure more of the system has made the
gerrit-jenkins-cfg-merge job unneeded and potentially dangerous to have
running since we're now configuring everything it does via JCasC.

Additionally, the gerrit-branch-lock has never been utilized by ORAN and
likely never will given their development process, as such there's no
reason for the job to be defined.

Change-Id: I0d2a759da894ad9e952eb9295a38fb82497eea31
Signed-off-by: Andrew Grimberg <agrimberg@linuxfoundation.org>