Added milestone applier rules for 1.34, removed 1.30

Author: mbianchidev

config/prow/plugins.yaml

@@ -474,10 +474,10 @@ milestone_applier:
     master: v1.34
   kubernetes/kubernetes:
     master: v1.34
+    release-1.34: v1.34
     release-1.33: v1.33
     release-1.32: v1.32
     release-1.31: v1.31
-    release-1.30: v1.30
   kubernetes/org:
     main: v1.34
   kubernetes/release: