Hide international pricing by default

It’s really big.

app/templates/views/pricing.html

@@ -61,6 +61,9 @@
       times the cost of messages to UK mobile numbers.
     </p>
 
+    <details>
+      <summary>International text message rates</summary>
+
       <div class="live-search" data-module="live-search" data-targets="#international-pricing .table-row">
         {{ textbox(
           search_form.search,
@@ -90,6 +93,8 @@
         {% endcall %}
       </div>
 
+    </details>
+
     <h2 class="heading-medium">
       Letters
     </h2>