Merge pull request #821 from brancz/gke

Add GKE patch

jsonnet/kube-prometheus/kube-prometheus-gke.libsonnet

+(import './kube-prometheus-managed-cluster.libsonnet') + {
+  _config+:: {
+    prometheusAdapter+:: {
+      config+: {
+        resourceRules:: null,
+      },
+    },
+  },
+
+  prometheusAdapter+:: {
+    apiService:: null,
+  },
+}