fix: update headline schema to not output a default text alignment unless explicitly set (#595)

Author: sghoweri

packages/components/bolt-headline/headline.schema.yml

@@ -25,7 +25,7 @@ properties:
   align:
     type: string
     description: Text alignment.
-    default: left
+    default: null
     enum:
       - left
       - center

packages/components/bolt-headline/src/_typography.twig

@@ -32,7 +32,7 @@
   baseClass,
   quoted ? baseClass ~ "--" ~ "quoted" : "",
   weight in weights ? baseClass ~ "--" ~ weight : "",
-  align and align != "" ? baseClass ~ "--" ~ align : "",
+  align and align != null ? baseClass ~ "--" ~ align : "",
   style in styles and type == "text" ? baseClass ~ "--" ~ style : "",
   size in sizes and type != "eyebrow" ? baseClass ~ "--" ~ size : "",
   transform in transformProps and transform != "" ? baseClass ~ "--" ~ transform : "",