testTableStructureMigration: be more independant of mariadb version

With 12f110d4 (testTableStructureMigration: update test after
mariadb 10.3.38, 2023-02-22) we changed the test to support mariadb >=
10.3.38 but it broke the test under 10.3.35.

This makes the test support both 10.3.35 and 10.3.38.