Show marker tickboxes for items with `true` as default

[zstadler]

Maputnik version: v1.7.0 Browser: Firefox OS: Windows

Description of the bug: The following style elements default to true:

• Fill layer's paint property fill-antialias
• Symbol layer's layout property text-keep-upright
• fill-extrusion layer's paint property fill-extrusion-vertical-gradient

However, the GUI representation of the default is a unchecked tickbox rather than a checked tickbox. As a result, when the default is used, the checkbox is clear, but the proprty is true/active.

Steps to reproduce the behavior:

1. Open https://maputnik.github.io/editor/#15/31.25102/35.12409
2. Upload this URL style.
3. Select the contour-label layer
4. Verify that
   • There is no value for the text-keep-upright propery in the JSON Editor
   • The Keep upright checkbox under Text layout properties is clear
   • The center of the map would show:
5. Click the Keep upright checkbox.
   • The checkbox is now marked
   • But the center of the map would look the same:
6. Click the Keep upright checkbox again
   • The checkbox is clear, as was when the style was loaded
   • But the text in center of the map would look different that initially:

Style file or style URL: https://raw.githubusercontent.com/IsraelHikingMap/VectorMap/044e90d16cdab4dcbb8749dd59dd417744c7d6a2/Styles/IHMcontour.json