Stop using mobile_top_margin in consultations

- headings have this unusual behaviour in consultation pages where the mobile top margin is much larger
- this is slightly odd and inconsistent behaviour, so we're removing this option from the heading component and applying custom spacing in these pages instead using existing component options

app/views/content_items/_attachments_list.html.erb

@@ -2,7 +2,7 @@
   <section id="<%= title.parameterize %>">
     <%= render 'govuk_publishing_components/components/heading',
       text: title,
-      mobile_top_margin: true
+      margin_bottom: 4
     %>
     <% add_gem_component_stylesheet("details") %>
     <% attachments_for_components.each do |details| %>

app/views/content_items/consultation.html.erb

@@ -57,7 +57,10 @@
         title: t("consultation.download_outcome"),
         attachments_for_components: @content_item.final_outcome_attachments_for_components
       %>
-      <%= render 'govuk_publishing_components/components/heading', text: t("consultation.detail_of_outcome"), mobile_top_margin: true %>
+      <%= render 'govuk_publishing_components/components/heading', {
+        text: t("consultation.detail_of_outcome"),
+        margin_bottom: 4,
+      } %>
       <div class="consultation-outcome-detail">
         <%= render 'govuk_publishing_components/components/govspeak', {
           direction: page_text_direction,
@@ -73,7 +76,7 @@
     %>
     <% if @content_item.public_feedback_detail %>
       <%= render 'govuk_publishing_components/components/heading', {
-        mobile_top_margin: true,
+        margin_bottom: 4,
         text: t("consultation.detail_of_feedback_received"),
       } %>
       <div class="consultation-feedback">
@@ -92,7 +95,7 @@
           <%= render 'govuk_publishing_components/components/heading', {
             heading_level: 2,
             id: "original-consultation-title",
-            mobile_top_margin: true,
+            margin_bottom: 4,
             text: t("consultation.original_consultation"),
           } %>
         </header>
@@ -136,7 +139,7 @@
 
     <div class="consultation-description">
       <%= render 'govuk_publishing_components/components/heading', {
-        mobile_top_margin: true,
+        margin_bottom: 4,
         text: t("consultation.description"),
       } %>