Update releasenotes publish job to use ensure-sphinx

The build-releasenotes role got updated so we need to switch to
ensure-sphinx here.

Change-Id: I1149f8b3d994f1d6af2cfce09a42a9bdc6865efd

playbooks/releasenotes/pre.yaml

@@ -1,4 +1,12 @@
 - hosts: all
   roles:
-    - ensure-reno
+    - role: bindep
+      bindep_profile: doc
+      bindep_dir: "{{ zuul_work_dir }}"
+    - role: ensure-sphinx
+      doc_building_packages:
+        - sphinx
+        - reno
+      # TODO(jaegerandi): Remove once all repos are fixed.
+      install_package: yes
     - revoke-sudo

playbooks/releasenotes/run.yaml

@@ -1,3 +1,4 @@
 - hosts: all
   roles:
+    - install-if-python
     - build-releasenotes