Blank Canvas Blocks: Fix List block font-family ponyfill variable

blank-canvas-blocks/assets/ponyfill.css

@@ -315,7 +315,7 @@ h1, h2, h3, h4, h5, h6 {
 
 ul,
 ol {
-	font-family: var(--wp--custom--list--fontFamily);
+	font-family: var(--wp--custom--list--font-family);
 	padding-left: var(--wp--custom--list--padding--left);
 }