Fix manual sorting in tl_metamodel.
Fix build matrix, it was checking always against the latest Contao 3.

This has been undiscovered for quite some time.
The build matrix was always checking against the latest Contao 3 version
instead of the latest 3.1, 3.2, 3.3 Versions.
Make Contao 3.3 non optional failure, we want to be compatible now.