Switch to horizon-nodejs4-jobs template

We need to switch these jobs to xenial. But while we're doing that,
let's shift to consuming a template managed in the horizon repo.

Depends-On: https://review.openstack.org/643198
Change-Id: I814466da98062ceb2bb30cf264451168c9a30693

.zuul.yaml

@@ -2,7 +2,7 @@
     templates:
       - openstack-lower-constraints-jobs-horizon
       - check-requirements
-      - nodejs4-jobs
+      - horizon-nodejs4-jobs
       - openstack-python-jobs-horizon
       - openstack-python35-jobs-horizon
       - publish-openstack-docs-pti
@@ -14,26 +14,6 @@
             required-projects:
               - openstack/horizon
         - horizon-openstack-tox-python3-django111
-        - nodejs-npm-run-lint:
-            vars:
-              node_version: 4
-            required-projects:
-              - openstack/horizon
-        - nodejs-npm-run-test:
-            vars:
-              node_version: 4
-            required-projects:
-              - openstack/horizon
     gate:
       jobs:
         - horizon-openstack-tox-python3-django111
-        - nodejs-npm-run-lint:
-            vars:
-              node_version: 4
-            required-projects:
-              - openstack/horizon
-        - nodejs-npm-run-test:
-            vars:
-              node_version: 4
-            required-projects:
-              - openstack/horizon