Correct docs-on-readthedocs to work with RTD publish

This patch set follows the guide [0] to leverage
the Zuul template [1] for correctly publishing RTD
doc changes via openstackci. Accordingly, all the
old code for doing this has been removed.

[0]
http://lists.openstack.org/pipermail/openstack-dev/2018-August/132836.html
[1]
https://docs.openstack.org/infra/openstack-zuul-jobs/project-templates.html#project_template-docs-on-readthedocs

Change-Id: Ibb38c5a420a2b06c0872840e054f7edc0b717cf6

.zuul.yaml

@@ -11,6 +11,10 @@
 # limitations under the License.
 
 - project:
+    templates:
+      - docs-on-readthedocs
+    vars:
+      rtd_webhook_id: '47578'
     check:
       jobs:
         - openstack-tox-pep8
@@ -26,7 +30,6 @@
         - airship-armada-docker-build-gate
     post:
       jobs:
-        - airship-armada-doc-publish
         - airship-armada-docker-publish
 
 - job:
@@ -107,41 +110,6 @@
         static:
           - latest
 
-- job:
-    name: airship-armada-doc-publish
-    description: |
-      Publish documentation on airship-armada.readthedocs.io
-    run: tools/gate/playbooks/readthedocs.yaml
-    nodeset: airship-armada-single-node
-    secrets:
-      - airship_armada_rtd_credential
-
-- secret:
-    name: airship_armada_rtd_credential
-    data:
-      id: !encrypted/pkcs1-oaep
-        - CUGL2+J0WfXsx2xyJRWs9QJHkEMlJkILygoYwJNlhotRm67UDhD1XZINU99BUkdwhow8F
-          uaFj14frfwH/lUDmXZWr5bZoAC5tDaaePABbdsSFrvCFXqdj+h0kw+0RVuIB1f2SQWCDH
-          J1geOd7kzqCGsrbUqGO1hBkkAVUItNN2GGZ/AdxUl/J4aFVbfHTdtXMiZ+WDw3dUhvF+m
-          xDHeSoHrbeLZCFrJIa+SJWgYIyA3uKSkRGMRZGrowkvo+rJXU0dZdWTXf12Vfzl4XLcit
-          EmAPm5g2bLT/IiOfqME+pTI2uTBSbPDkLiPI2foj+FU1Cpnzwc0aZyEzThm99z7InRJAM
-          aODu1yBEoyufa9FxE7X92pzi9L0fj0ehjLUPlurd04w/41pWj8kvv+joREXxq4b8UXWCk
-          0XFgnhNqYEnodSTzxTG7iL1n7KHrulI1SHOeyaWZCyFFHvkIV2a5x9it09uR7Mvs3X9ZE
-          Zf1nkvY4qttQXYmgrQm4IoJ3P0Z5pKwF6rma+bUUYuBJ/PdESJ1CUX8WnjvSLUVmxvlW/
-          dUz+x9eTOGIkvdr/l2kyYFGV3jrRJnNvWN170InbyujB0Oj5do5HyqPqyZ2RcQs+Tlk8n
-          1bIsPVdS0d6dvfJjVqbb06W57ar173jJ1BIW6D1p+YyRPyg1D6FTVRCcReFHu0=
-      token: !encrypted/pkcs1-oaep
-        - pR4aUNome/tdBk+HM8uNZOAOqiuMn6dWoeOTqehrtC1pf2WwQU/Cx0lqochjDfdIBSjI0
-          25zEdrr8/Jl2HhMx7jX/Swm6xySQ0LEkiZ8DR+I1C//qTrazwKgUR1s52h1W/HCN1a7nD
-          zwlboH46XPrD04JCl266XmtYL7gQb+9h9jPzpXaatQUplqRpDDOg7jhc8FuSVYiRFaVc1
-          GxKDvcnMEZT5H9pPGHzn4uJHyv8p/3pKNLROSWY/W7TP6V6ydXXG30jsPSPFUT45Z7PZ5
-          SE6+9WFqkxD6/GKj0YH4t9cu7oHmltX2TMbkdZHlDa2mtq7R31c9gPiianP3bTu3RRSdT
-          B2KdMrDaJD08+Lz4DnuX0NAl5LKTxyybHN21zHLhEiAsP/ZX46xhLNpvYTkCjGGKKA7JT
-          2K6YLrzLoTUuQV0C0/0xX49l6aRHG4mOtlHC1OUXecQPHh7mzDX9Ro/mzKynknsXsFiaD
-          uT1PKnoN8Lj0rWk50/7uB6ycw2LJVCt3RtFimBVvkJtI2RJ7FjePnNZF9tVZ0FFyiGpwO
-          0pKkh4jV/8VuS+vpY5ehigvzGR1nC3ymF+10kNLiOutzRXFssbR0eDeW8T816is81azea
-          FU8taphOcrrw4rB6g5qdEO6wierpuO6uOFfOMeSrSxx2hhMvROTJA2OuwxpB/8=
-
 - secret:
     name: airship_armada_quay_creds
     data: