Improve language handling for MathCAT braille (#19375)
Split from #19227. Follow-up of #19368.
Summary of the issue:
The automatic Braille entry for Finnish was incorrect.
Several languages could have more reasonable Braille defaults.
Description of how this pull request fixes the issue:
Simplify (key on base language only, not region codes), fix "fi", and expand Braille auto language table.
