On Ubuntu 2004, post-merge Python unit tests are run on in the single Evergreen task 'unit-test-extra-long', which is executed on ubuntu2004-large instances.

However, PR/patch testing for the Python unit tests are run in a series of bucket tasks (named unit-test-long-bucket00 to unit-test-long-bucket11) on ubuntu2004-test (aka ubuntu2004-small) instances.

Some test fail on the small instances. For example test_txn13.test_txn13.test_large_values(integer-row.4gb).

This ticket will fix this issue by changing the PR/patch Python unit tests to run on ubuntu2004-large instances.