Respect message ordering

See https://spec.matrix.org/v1.11/application-service-api/#timestamp-massaging
for why this might be needed.
This removes concurrency for handleMessage calls, which is probably not
what we want.

src/app.ts

@@ -42,13 +42,13 @@ async function loadRcExport(entity: Entity) {
 
       case Entity.Messages:
         if (!item.tmid) {
-          queue.push(limit(() => handleMessage(item)))
+          await handleMessage(item)
         }
         break
 
       case Entity.ThreadMessages:
         if (item.tmid) {
-          queue.push(limit(() => handleMessage(item)))
+          await handleMessage(item)
         }
         break