Remove trusty docs publish job
As part of the docs-migration, we already changed the publish job to
only run on xenial - all official repos have eol'ed mitaka. Thus, remove
the job definition for trusty as well.
name: openstack-publish-jobs
jobs:
- '{name}-docs-unified-{node}'
- node:
- - ubuntu-trusty
- - ubuntu-xenial
+ node: ubuntu-xenial
- job-group:
name: openstack-releasenotes-jobs
