[18.0.0-proposed]Use branch specific renovate config

[gibizer]

It depends on https://github.com/openstack-k8s-operators/renovate-config/pull/17 (but I cannot add a Depends-On as that hurts RDO zuul) Related: OSPRH-8355

[gibizer]

/hold

[openshift-ci[bot]]

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[viroel]

/retest-required

[openshift-ci[bot]]

@gibizer: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/openstack-operator-build-deploy	f5e58e85ea7c6b15b469e9248f8f899d1b43ec5f	link	true	/test openstack-operator-build-deploy

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[gibizer]

we won't try this on 18.0.0-proposed