TripleO: Remove unused project template

The tripleo-puppet-standalone template is not really used in any
module repos, because each repo defines its own standalone job.

Conflicts:
	zuul.d/tripleo.yaml

Backport note:
stable/xena and yoga are skipped because tripleo jobs have been removed
from these branches.

Change-Id: I8525806576e1108a936e5b036859671794f304de
(cherry picked from commit 4a70a28935)
(cherry picked from commit b695e7dc5d)

zuul.d/tripleo.yaml

@@ -51,13 +51,3 @@
       featureset_override:
         standalone_environment_files:
           - 'environments/low-memory-usage.yaml'
-
-- project-template:
-    name: tripleo-puppet-standalone
-    check:
-      jobs:
-        - tripleo-puppet-ci-centos-9-content-provider
-        - tripleo-puppet-ci-centos-9-standalone:
-            vars: *undercloud_consumer_vars
-            dependencies:
-              - tripleo-puppet-ci-centos-9-content-provider