infra: update renovate labels

.github/renovate.json5

@@ -1,7 +1,7 @@
 {
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": ["config:base", "schedule:weekly", "group:allNonMajor"],
-  "labels": ["dependencies"],
+  "labels": ["c: dependencies"],
   "rangeStrategy": "bump",
   "packageRules": [
     {
@@ -59,6 +59,6 @@
     }
   ],
   "vulnerabilityAlerts": {
-    "labels": ["security"]
+    "labels": ["c: security"]
   }
 }