Remove Rubik font from heading definition (#7267)

block-canvas/theme.json

@@ -339,7 +339,6 @@
 			},
 			"heading": {
 				"typography": {
-					"fontFamily": "var(--wp--preset--font-family--rubik)",
 					"fontWeight": "400",
 					"lineHeight": "1.125"
 				}