Favour the appHeading macro over hard-coded HTML

Co-authored-by: Paul Robert Lloyd <paulrobertlloyd@users.noreply.github.com>

Author: malross

app/views/book-into-a-clinic/form/check-answers.njk

@@ -12,9 +12,11 @@
     title: title
   }) }}
 
-  <h2 class="nhsuk-heading-m">
-    Child details
-  </h2>
+  {{ appHeading({
+    title: "Child details",
+    level: 2,
+    size: "m"
+  }) }}
 
   <dl class="nhsuk-summary-list">
     <div class="nhsuk-summary-list__row">