Add back _config.runbookURLPattern for Thanos Sidecar rules

jsonnet/kube-prometheus/components/prometheus.libsonnet

@@ -59,6 +59,7 @@ function(params) {
   mixinThanos::
     (import 'github.com/thanos-io/thanos/mixin/alerts/sidecar.libsonnet') +
     (import 'github.com/kubernetes-monitoring/kubernetes-mixin/lib/add-runbook-links.libsonnet') + {
+      _config+:: p._config.mixin._config,
       targetGroups: {},
       sidecar: {
         selector: p._config.mixin._config.thanosSelector,