"Fix" a race condition with store disposal in fixtures.

https://github.com/the-draupnir-project/Draupnir/issues/927.

test/integration/fixtures.ts

@@ -60,6 +60,7 @@ async function cleanUpTopLevelStores(storagePath: string) {
       }
     })
   );
+  //
 }
 
 // When Draupnir starts (src/index.ts) it clobbers the config by resolving the management room
@@ -106,6 +107,8 @@ export const mochaHooks = {
       await this.toggle?.stopEverything();
       draupnirClient()?.stop();
       this.stores?.dispose();
+      // With regret, please see https://github.com/the-draupnir-project/Draupnir/issues/927.
+      await new Promise((resolve) => setTimeout(resolve, 50));
       if (this.draupnir !== undefined) {
         await Promise.all([
           this.draupnir.client.setAccountData(