jenkins systemuser call was invalid

When I have migrated the jenkins user definition from `user` to
`systemuser` define, I forgot to drop the 'gid' parameter.  The require
is not needed too since that is included in the `systemuser` def.

Caused:
Invalid parameter gid at modules/jenkins/manifests/user.pp:12

Change-Id: I55a3ff9af00362b362411704c9e691a8dee28594
Merge "jenkins systemuser call was invalid" into production