[SUGGESTION][EDITOR] Remove the "Special Graph" from the level properties

[GigaLem]

Since we can get a "VGASPEC" effect through mixing tilesets, why is the Special grap location still there? I can't even click on it to add VGAspecs

[namida]

To allow loading existing levels that use them, and see their coordinates, for the purpose of switching those levels to the newer system. Effectively, it's read/preserve only, the only edit that's allowed is removing the special graphic altogether.

[namida]

By now people have had plenty of time to upgrade their levels, so I'm removing support altogether for the next update (it was probably already pretty broken anyway).

In the event that anyone still has old levels that haven't been upgraded, use an older version of the editor (up to V10.12.12) to upgrade them.