Skip functional tests for .pre-commit-config.yaml update

... because the file is used only in pep8 jobs.

Change-Id: Ifc044dd6d5715623ef29f9102221fada52cc0fa3
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>

.zuul.yaml

@@ -25,6 +25,7 @@
       tox_envlist: all
     irrelevant-files: &zaqar-irrelevant-files
       - ^\.gitreview$
+      - ^\.pre-commit-config\.yaml$
       - ^(test-|)requirements.txt$
       - ^.*\.rst$
       - ^api-ref/.*$