Update test_group_4 to include changing state after rollback

[qirh]

As mentioned by others in Issue #8, I believe there is a bug in the test file for Level 4.

Order of Operations

1. ["FILE_UPLOAD_AT", "2021-07-01T12:00:00", "Initial.txt", "100kb"]
2. ["FILE_UPLOAD_AT", "2021-07-01T12:05:00", "Update1.txt", "150kb", 3600]
3. ["FILE_GET_AT", "2021-07-01T12:10:00", "Initial.txt"]
4. ["FILE_COPY_AT", "2021-07-01T12:15:00", "Update1.txt", "Update1Copy.txt"]
5. ["FILE_UPLOAD_AT", "2021-07-01T12:20:00", "Update2.txt", "200kb", 1800]
6. ["ROLLBACK", "2021-07-01T12:10:00"]
7. ["FILE_GET_AT", "2021-07-01T12:25:00", "Update1.txt"]
8. ["FILE_GET_AT", "2021-07-01T12:25:00", "Initial.txt"]
9. ["FILE_SEARCH_AT", "2021-07-01T12:25:00", "Up"]
10. ["FILE_GET_AT", "2021-07-01T12:25:00", "Update2.txt"]

Issue After step 6 (ROLLBACK), the file Update2.txt should not exist because it was uploaded at 2021-07-01T12:20:00, which is after the rollback timestamp 2021-07-01T12:10:00.

Since the system is rolled back to the state as of 2021-07-01T12:10:00, any files uploaded after this timestamp should no longer exist. However, the test case appears to assume Update2.txt is still accessible after the rollback, which contradicts the expected behavior.