Add irrelevant-files for openstack-tox-py312

We want the same parameters here as for the other tox jobs. Note that
the job is currently still non-voting, will need to add the same params
in the gate pipeline once that changes.

Change-Id: I063d9c82755f805510c28fb168f582775fcb1ff7

.zuul.yaml

@@ -45,6 +45,11 @@
               - ^data/.*$
               - ^deliverables/.*$
               - ^doc/.*$
+        - openstack-tox-py312:
+            irrelevant-files:
+              - ^data/.*$
+              - ^deliverables/.*$
+              - ^doc/.*$
         - openstack-tox-pep8:
             irrelevant-files:
               - ^data/.*$