zuul: use only RE2 syntax

Zuul has deprecated Perl-style regex expressions in favor of RE2,
and our zuul config file is generating warnings [0], so let's
fix this now before it becomes an issue.

[0] https://zuul.opendev.org/t/openstack/config-errors?project=openstack%2Fcinder-tempest-plugin

Depends-on: https://review.opendev.org/c/openstack/cinderlib/+/896658

Change-Id: I90c9cde9e825b49b94202708e7bffc3556288a6d
1 file changed