UI: Remove cutoff text in popovers for 2.90 release

Many of these popovers could use a design pass in 2.91, but for 2.90 we
don't want to change any UI strings at this point, so the best way to
solve the cutoff text is to widen the popovers. Sadly this won't affect
popovers when other languages besides English have longer strings, but
solving that is a much larger task.

Another benefit is that tweaking sculpt / paint brush options feels much
less cramped with slightly wider popovers.

I only know of one string that is still slightly cutoff by default with
this patch, the "Max Element Distance" property of the pose brush in the
sculpt mode brush settings popover. But I didn't think it was worth
widening that popover more to deal with that one case.

Differential Revision: https://developer.blender.org/D8575

release/scripts/startup/bl_ui/properties_paint_common.py

@@ -313,6 +313,7 @@ class TextureMaskPanel(BrushPanel):
 class StrokePanel(BrushPanel):
     bl_label = "Stroke"
     bl_options = {'DEFAULT_CLOSED'}
+    bl_ui_units_x = 13
 
     def draw(self, context):
         layout = self.layout