fix: disable renovate lockFileMaintenance (uv not supported in runner)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: mldangelo

renovate.json

@@ -2,5 +2,8 @@
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": [
     "local>promptfoo/renovate-config"
-  ]
+  ],
+  "lockFileMaintenance": {
+    "enabled": false
+  }
 }