Update icon to 24

In the dev tools the viewBox should be 24. @hashicorp/flight-icons now uses 16 as default.

addons/core/addon/components/doc-link/index.hbs

@@ -4,5 +4,5 @@
   target="_blank"
   rel="noreferrer noopener"
   title={{t "actions.get-topic-help"}}>
-  <Rose::Icon @name="flight-icons/help-16" @size={{@iconSize}} />
+  <Rose::Icon @name="flight-icons/help-24" @size={{@iconSize}} />
 </a>