Use python3 for docs publication

Change-Id: I40ba4939c09d9f3f5105e37a23090dad6cabdbdb
Depends-On: I2d0222225f4ae6c45d09f9352c256062e2535d63
diff --git a/.zuul.yaml b/.zuul.yaml
index a87c196..7473ad3 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -65,7 +65,5 @@
         - zuul-stream-functional
     post:
       jobs:
-        - publish-openstack-sphinx-docs-infra:
-            vars:
-              sphinx_python: python3
+        - publish-openstack-sphinx-docs-infra-python3
         - publish-openstack-python-branch-tarball