Restore insignia fix

[Goober5000]

This will need to be done for 26.0 or 26.2. From #7196:

Apparently, two or so FSPort retail models had broken POFs that caused problems with the fix, so roll back the insignias to being incorrectly lit and faded for now, until someone has time to work around the broken models.

To fix the insignia bugs properly, one needs to revert this revert again, but make sure to analyze the insignia geometry in modelread.cpp, splitting non-adjacent faces so that multiple insignias in a single slot are correctly split into multiple insignia instances.

Depending on how difficult a code-only solution is, and how widespread the model bugs are, it might be less work to fix the affected models.