SERVER-109626 will introduce a new test file jstests/sharding/query/change_streams/change_stream_transaction_sharded_commit_timestamp.js which is a clone of the existing file jstests/sharding/query/change_streams/change_stream_transaction_sharded.js with added checks for the commitTimestamp change event field.

Cloning the original file was necessary as part of SERVER-109626 because it will introduce a behavior change for the conditions under which the commitTimestamp will be emitted. From SERVER-109626 onwards, this requires setting a new change stream flag showCommitTimestamp. This flag is not understood by older mongod versions.
In order to keep the existing test file running in multiversion tests and keep that test coverage, SERVER-109626 introduced a new test file for the additional commit timestamps. This new test file is currently excluded from multi-version testing.

Once v9.0 becomes last LTS, we can clean up. We can then remove jstests/sharding/query/change_streams/change_stream_transaction_sharded.js entirely and enable multi-version testing for jstests/sharding/query/change_streams/change_stream_transaction_sharded_commit_timestamp.js instead.
Finally, we can rename the latter file to {jstests/sharding/query/change_streams/change_stream_transaction_sharded.js}} again.