test(fast-inbox): drop isOpen from the inbox bucket ref fixture (A-1381)

Author: spalladino

yarn-project/stdlib/src/messaging/inbox_bucket.test.ts

@@ -34,7 +34,6 @@ describe('InboxBucketRef', () => {
       timestamp: 1_650_000_000n,
       msgCount: 3,
       lastMessageIndex: 29n,
-      isOpen: true,
     };
     const ref = InboxBucketRef.fromBucket(bucket);
     expect(ref.bucketSeq).toBe(bucket.seq);