Adjusted theme.json to match expected shape (#3513)

seedlet-blocks/experimental-theme.json

@@ -7,8 +7,8 @@
 			"area": "footer"
 		}
 	},
-	"global": {
-		"settings": {
+	"settings": {
+		"defaults": {
 			"color": {
 				"gradients": [
 					{