docs(run-engine): correct the ckExpireTtlLua sharing comment

Post-merge the flag-off TTL sweep is main's inline gated version, so ckExpireTtlLua
is used only by the vtime variant now. Note the deferred gate-release integration.

Author: 1stvamp

internal-packages/run-engine/src/run-queue/index.ts

@@ -950,7 +950,9 @@ ${QUEUE_METRICS_CK_ENQUEUE_GAUGE_LUA}
 return __qmret(0)
       `;
 
-// Shared by the ck TTL sweep and its virtual-time variant.
+// Used only by the ck TTL sweep's virtual-time variant. INTERIM: the flag-off
+// expireTtlRunsTracked carries main's inline gated version; queue-gate release is not yet
+// threaded through this vtime template (follow-up, alongside the vtime dequeue).
 const ckExpireTtlLua = (v: CkParts<"args" | "drain">) => `
 local ttlQueueKey = KEYS[1]
 local keyPrefix = ARGV[1]