remove the legacy driver job for keystone

we are removing the stable driver interfaces in the ocata
release [1] and no longer need the jobs.

[1] https://review.openstack.org/#/c/375928/7/tox.ini

Change-Id: Ic4b067b472dad3b8231cb2397abbb92a52939c31

jenkins/jobs/projects.yaml

@@ -5990,11 +5990,6 @@
           node:
             - ubuntu-trusty
             - ubuntu-xenial
-      - gate-{name}-tox-db-{envlist}-{node}:
-          envlist: legacy_drivers
-          node:
-            - ubuntu-trusty
-            - ubuntu-xenial
       - '{pipeline}-tempest-dsvm-keystone-eventlet-full{job-suffix}':
           pipeline: gate
           job-suffix: ''

zuul/layout.yaml

@@ -2640,9 +2640,6 @@ jobs:
   - name: ^gate-keystone-tox-patch_cover-ubuntu-(trusty|xenial)$
     voting: false
 
-  - name: ^gate-keystone-tox-db-legacy_drivers-ubuntu-trusty$
-    branch: ^stable/mitaka.*$
-
   - name: gate-tempest-dsvm-keystone-uwsgi-full-ubuntu-trusty-nv
     branch: ^stable/mitaka$
 
@@ -10401,8 +10398,6 @@ projects:
       - name: api-ref-jobs
     check:
       - gate-keystone-tox-bandit-ubuntu-trusty
-      - gate-keystone-tox-db-legacy_drivers-ubuntu-trusty
-      - gate-keystone-tox-db-legacy_drivers-ubuntu-xenial
       - gate-keystone-dsvm-functional-ubuntu-xenial
       - gate-keystone-dsvm-functional-v3-only-ubuntu-xenial-nv
       - gate-tempest-dsvm-keystone-eventlet-full
@@ -10414,8 +10409,6 @@ projects:
     gate:
       - gate-keystone-dsvm-functional-ubuntu-xenial
       - gate-keystone-tox-bandit-ubuntu-trusty
-      - gate-keystone-tox-db-legacy_drivers-ubuntu-trusty
-      - gate-keystone-tox-db-legacy_drivers-ubuntu-xenial
     experimental:
       - gate-grenade-dsvm-forward
       - gate-rally-dsvm-keystone