Problem/Motivation
In #3107113: [policy] Decide on MySQL/MariaDB/Percona Server version support status for Drupal 9 the general direction of raising MySQL requirements to 5.7 and MariaDB requirements to 10.2 was agreed on.
Proposed resolution
Raise version requirements.
It was discussed that this may require resolving #2985788: Add a separate MariaDB driver first, but that does not seem to be the case.
Remaining tasks
Raise version requirements.
Update documentation.
User interface changes
None.
API changes
None.
Data model changes
None.
Release notes snippet
Raised the minimum MySQL version to 5.7 and MariaDB version to 10.2 in Drupal 9. See https://www.drupal.org/node/3119156