Blockbase: Use variable for heading font size (#5101)

blockbase/theme.json

@@ -535,7 +535,7 @@
 					"fontFamily": "var(--wp--preset--font-family--heading-font)",
 					"fontWeight": "var(--wp--custom--heading--typography--font-weight)",
 					"lineHeight": "var(--wp--custom--heading--typography--line-height)",
-					"fontSize": "32px"
+					"fontSize": "var(--wp--preset--font-size--huge)"
 				},
 				"spacing": {
 					"margin": {