mitaka-eol: Remove unused jobs

bifrost and monasca do not need trusty jobs in zuul anymore, remove job
definitions.

Change-Id: I1468d89d0c264d3b967129ae2419df4cfb38e456

jenkins/jobs/bifrost.yaml

@@ -111,7 +111,6 @@
     node:
       - centos-7
       - opensuse-422
-      - ubuntu-trusty
       - ubuntu-xenial
     jobs:
       - gate-bifrost-integration-tinyipa-{node}

jenkins/jobs/monasca.yaml

@@ -62,9 +62,7 @@
     name: 'tempest-monasca-full-jobs'
     jobs:
       - 'gate-tempest-dsvm-monasca-{lang}-{backend}-full-{node}{suffix}':
-          node:
-            - ubuntu-trusty
-            - ubuntu-xenial
+          node: ubuntu-xenial
           suffix:
             - ''
             - '-nv'