Remove publish-to-pypi-python3

The template has been obsoleted, we use publish-to-pypi everywhere
again.

Needed-By: https://review.openstack.org/615242
Depends-On: https://review.openstack.org/615239
Depends-On: https://review.openstack.org/615296
Depends-On: https://review.openstack.org/615291
Change-Id: I606dcd8086615e4fd89fa379bf287d96badb0eed

zuul.d/project-templates.yaml

@@ -201,32 +201,6 @@
             dependencies:
               - release-openstack-python
 
-- project-template:
-    name: publish-to-pypi-python3
-    description: |
-      Publish a Python package to PyPI, then send release announcement
-      emails and propose updates to upper-constraints as needed.
-
-      This is now obsolete, publish-to-pypi uses the same definition.
-    check:
-      jobs:
-        - test-release-openstack-python3
-    gate:
-      jobs:
-        - test-release-openstack-python3
-    pre-release:
-      jobs:
-        - release-openstack-python3
-    release:
-      jobs:
-        - release-openstack-python3
-        - announce-release:
-            dependencies:
-              - release-openstack-python3
-        - propose-update-constraints:
-            dependencies:
-              - release-openstack-python3
-
 - project-template:
     name: publish-xstatic-to-pypi
     description: |