Re-enable Arabic fallback font when it no longer causes line height issues

[hhyyrylainen]

Adding Arabic fallback font causes all GUI labels to take up a bunch of extra vertical space. That's why the fallback font is currently unset. It'd be good to find the problem with this and re-enable it.

This is likely related to: godotengine/godot#79858 though my experience is that that seems to already happen (i.e. specifying a fallback font causes the vertical space to appear even before any fallback characters are used).