revert the change to expect the 'creationDate' always as type Date

backend/src/federation/client/1_0/logging/PublicCommunityInfoLogging.view.ts

@@ -11,7 +11,7 @@ export class PublicCommunityInfoLoggingView extends AbstractLoggingView {
     return {
       name: this.self.name,
       description: this.self.description,
-      creationDate: this.self.creationDate,
+      creationDate: this.dateToString(this.self.creationDate),
       publicKey: this.self.publicKey,
     }
   }