refactor: slip another one in

With async-await,
we can more clearly show that you send the info either way,
only awaiting the promise is guarded.

lib/elm-app-worker.js

@@ -31,14 +31,12 @@ if (parentPort) {
  * @returns {void}
  */
 function subscribe(parentPort) {
-  parentPort.on('message', ([port, data]) => {
+  parentPort.on('message', async ([port, data]) => {
     if (port === 'startReview' || port === 'startGeneratingSuppressions') {
-      loadCachePromise.then(() => {
-        app.ports[port].send(data);
-      });
-    } else {
-      app.ports[port].send(data);
+      await loadCachePromise;
     }
+
+    app.ports[port].send(data);
   });
 
   app.ports.requestReadingFiles.subscribe((data) => {