Not allowed "theme" property added to settings.spacing.spacingScale

[valentin-grenier]

If a spacing scale is defined in settings.spacing.spacingScale and if the user saves its theme to files from the site editor, a theme property is added to spacingScale as a child. It does not break the theme but the property is not allowed by schema ("Property theme is not allowed.").

Identified bug:

"spacingScale": {
	"theme": {
		"increment": 16,
		"mediumStep": 32,
		"operator": "+",
		"steps": 7,
		"unit": "px"
	}
},

Should be:

"spacingScale": {
	"increment": 16,
	"mediumStep": 32,
	"operator": "+",
	"steps": 7,
	"unit": "px"
},