[18.0.0-proposed]Use branch specific renovate config

[gibizer]

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

[gibizer]

/hold

[openshift-ci]

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[viroel]

/retest-required

[openshift-ci]

@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	f5e58e8	link	true	/test openstack-operator-build-deploy

Full PR test history. Your PR dashboard.

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