mitaka-eol: Remove trusty from lib-forward-testing
All jobs have been removed already, adjust job-group to not define
unused jobs. With mitaka EOL we do not need to forward test on mitaka
anymore.
jobs:
- '{pipeline}-tempest-dsvm-neutron-src-{name}-{node}{suffix}':
pipeline: gate
- node:
- - ubuntu-trusty
- - ubuntu-xenial
+ node: ubuntu-xenial
suffix: ''
branch-override: default
