Moved Jenkins doc to jenkins-job-builder-config repo

The Jenkins configuration is now handled independently:

https://github.com/zeljkofilipin/jenkins-job-builder-config/commit/dc594d23a12aed4215e3f89c3a7bed43d490c1cc

Change-Id: Ib25f3334b85a3519d0db641b551af8cc524de91f