chore(renovate): don't age-gate submodule digest bumps

protocol main moves faster than the repo-wide 2-week minimumReleaseAge,
so the protocol submodule digest never aged out of "Pending Status
Checks" and Renovate never opened a PR for it.

Author: u9g

renovate.json

@@ -38,6 +38,10 @@
       "matchManagers": ["git-submodules"],
       "matchDepNames": ["livekit-rtc/rust-sdks"],
       "enabled": false
+    },
+    {
+      "matchManagers": ["git-submodules"],
+      "minimumReleaseAge": null
     }
   ]
 }