fix(proto): bump submodule to #927 (disable/DISABLED) and drop stale Marti prune

Moves core/proto to PR #927 head (c834f6b), which adds LockdownAuth.disable
and LockdownStatus.State.DISABLED on top of develop. That tree has no
meshtastic.Marti message, so the Marti prune left over from the master merge
was unused and broke generateCommonMainProtos; remove it.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

core/proto/build.gradle.kts

@@ -120,7 +120,6 @@ wire {
     prune("meshtastic.GeoPointSource")
     prune("meshtastic.TakTalkMessage")
     prune("meshtastic.TakTalkRoomData")
-    prune("meshtastic.Marti")
 }
 
 // Modern KMP publication uses the project name as the artifactId by default.