Drop nodejs4 job

As Migration to bionic is completed or nodejs10 job running.
So we not required nodejs4 job anymore.

Change-Id: I179706cbd53b33f15bdc485168a7eba09fc788e5

.zuul.yaml

@@ -94,28 +94,6 @@
       - ^setup.cfg$
       - ^tools/.*$
 
-- job:
-    name: nodejs4-npm-run-lint
-    parent: nodejs-npm-run-lint
-    description: |
-      Run lint using Node 4 for horizon plugins.
-    vars:
-      node_version: 4
-    nodeset: ubuntu-xenial
-    required-projects:
-      openstack/horizon
-
-- job:
-    name: nodejs4-npm-run-test
-    parent: nodejs-npm-run-test
-    description: |
-      Run test using Node 4 for horizon plugins.
-    vars:
-      node_version: 4
-    nodeset: ubuntu-xenial
-    required-projects:
-      openstack/horizon
-
 - job:
     name: nodejs10-npm-run-lint
     parent: nodejs-npm-run-lint
@@ -138,30 +116,6 @@
     required-projects:
       openstack/horizon
 
-- project-template:
-    name: horizon-nodejs4-jobs
-    description: |
-      Run lint and test jobs using Node 4 for horizon plugins.
-    check:
-      jobs:
-        - nodejs4-npm-run-lint
-        - nodejs4-npm-run-test
-    gate:
-      jobs:
-        - nodejs4-npm-run-lint
-        - nodejs4-npm-run-test
-
-- project-template:
-    name: horizon-nodejs4-jobs-nonvoting
-    description: |
-      Run lint and test jobs using Node 4 for horizon plugins.
-    check:
-      jobs:
-        - nodejs4-npm-run-lint:
-            voting: false
-        - nodejs4-npm-run-test:
-            voting: false
-
 - project-template:
     name: horizon-nodejs10-jobs
     description: |
@@ -189,7 +143,6 @@
 - project:
     templates:
       - check-requirements
-      - horizon-nodejs4-jobs
       - horizon-nodejs10-jobs
       - openstack-lower-constraints-jobs
       - openstack-python-jobs