fix(fill_db_data.py): update NULL_VALUES_SUPPORT_ENTERPRISE_MIN_VERSION to 2021.1.3
fix(fill_db_data.py): update NULL_VALUES_SUPPORT_ENTERPRISE_MIN_VERSION to 2021.1.3

Currently upgrade test from 2021.1 to 2021.1.latest failed in
fill_db_data check.

- AssertionError: query 'SELECT * FROM null_support_test_old_version
                   WHERE k = null' is not valid

Because one scylla commit was just backported to branch-2021.1, so null
query will be supported from 2021.1.3.
- scylla-enterprise/commit/0584e557cca0cd4fd84807f03a2ec95cd8ec1878

Signed-off-by: Amos Kong <eb01d8f828a6c9a20be4534e72e049aaf41503df@scylladb.com>

scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests