test: Fix type error in `test_create_table` and `test_update_table`

[xiaozhiyan]

Hi there, I've pulled main branch at a6d98c3 and found that tests test_create_table and test_update_table would fail due to type error.

error[E0277]: can't compare `{integer}` with `chrono::DateTime<chrono::Utc>`
    --> crates/catalog/rest/src/catalog.rs:1281:9
     |
1281 |         assert_eq!(1657810967051, table.metadata().last_updated_ms());
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no implementation for `{integer} == chrono::DateTime<chrono::Utc>`

error[E0277]: can't compare `{integer}` with `chrono::DateTime<chrono::Utc>`
    --> crates/catalog/rest/src/catalog.rs:1453:9
     |
1453 |         assert_eq!(1657810967051, table.metadata().last_updated_ms());
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no implementation for `{integer} == chrono::DateTime<chrono::Utc>`

CI: https://github.com/apache/iceberg-rust/actions/runs/6978413094/job/18989781732

We may need to add .timestamp_millis() or use Utc.timestamp_millis_opt(1657810967051).unwrap() in the following two lines.

• a6d98c3#diff-cb9d997d5104f8406186a80782bdc7f9bde4426ec307b73ce710d94bfae5ac5aR1281
• a6d98c3#diff-cb9d997d5104f8406186a80782bdc7f9bde4426ec307b73ce710d94bfae5ac5aR1453