Adjust branch rules for 3.x branch (#234)

Author: mallardduck

.github/renovate.json

@@ -19,9 +19,13 @@
   ],
   "packageRules": [
     {
-      "matchBaseBranches" : ["main", "release/v3.x"],
+      "matchBaseBranches" : ["main"],
       "extends" : ["github>rancher/renovate-config:rancher-main#release"]
     },
+    {
+      "matchBaseBranches" : ["release/v3.x"],
+      "extends" : ["github>rancher/renovate-config:rancher-2.11#release"]
+    },
     {
       "matchBaseBranches" : ["release/v2.x"],
       "extends" : ["github>rancher/renovate-config:rancher-2.10#release"]