Configure to only use single base font.

blank-canvas-blocks/experimental-theme.json

@@ -107,14 +107,9 @@
 				],
 				"fontFamilies": [
 					{
-						"fontFamily": "Helvetica, Arial, sans-serif",
-						"slug": "primary",
-						"name": "Primary"
-					},
-					{
-						"fontFamily": "Georgia, Times, serif",
-						"slug": "secondary",
-						"name": "Secondary"
+						"fontFamily": "var(--font-base, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif)",
+						"slug": "base",
+						"name": "Base"
 					}
 				]
 			},
@@ -151,7 +146,7 @@
 				},
 				"button": {
 					"font-weight": "600",
-					"font-family": "var(--wp--preset--font-family--primary)",
+					"font-family": "var(--wp--preset--font-family--base)",
 					"font-size": "var(--wp--preset--font-size--small)",
 					"border-radius": "4px",
 					"color": {
@@ -186,7 +181,7 @@
 			"typography": {
 				"fontSize": "var(--wp--preset--font-size--normal)",
 				"lineHeight": "var(--wp--custom--line-height--body)",
-				"fontFamily": "var(--wp--preset--font-family--primary)"
+				"fontFamily": "var(--wp--preset--font-family--base)"
 			}
 		},
 		"core/button": {