documentation

Pull request #1643: feature/ZBXNEXT-8984-6.0-D. Updated maximum supported MySQL version to 8.3.

Merge in WEB/documentation from feature/ZBXNEXT-8984-6.0-D to release/6.0

* commit 'dc87b8049d438dc0d4a5e3e446008b90d164861f':
  [ZBXNEXT-8984] Updated maximum supported MySQL version to 8.3