Editor: Correct padding value for styles.elements.spacing in theme.json.

Each of the four directions must be defined separately based on the schema, otherwise the code editor will throw a validation error.

Follow-up to [54162].

Props aslamdoctor, wildworks.
Fixes #63374.

git-svn-id: https://develop.svn.wordpress.org/trunk@60217 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-includes/theme.json

@@ -373,7 +373,12 @@
 					"background": "#32373c"
 				},
 				"spacing": {
-					"padding": "calc(0.667em + 2px) calc(1.333em + 2px)"
+					"padding": {
+						"top": "calc(0.667em + 2px)",
+						"right": "calc(1.333em + 2px)",
+						"bottom": "calc(0.667em + 2px)",
+						"left": "calc(1.333em + 2px)"
+					}
 				},
 				"typography": {
 					"fontSize": "inherit",