fix(renovate): silence the GitHub-token warning for deps disabled on purpose

The only github-hosted deps left are the generated-workflow action pins
and marimo, both disabled by packageRules (gen_config.py and
marimo_latest.py own them). Renovate still lists them as needing a
token, so the Dependency Dashboard kept a standing warning.

renovate.json

@@ -8,6 +8,7 @@
   "prHourlyLimit": 0,
   "minimumReleaseAge": "7 days",
   "fetchChangeLogs": "off",
+  "githubTokenWarn": false,
   "ignorePaths": [
     "**/node_modules/**",
     "**/bower_components/**",