improve collapsable preface instruction clarity

scipost_django/proceedings/templates/proceedings/_description.html

@@ -105,7 +105,8 @@
   <details class="border border-primary bg-primary bg-opacity-10 p-2 my-4">
     <summary>
       <div class="p-2 border-bottom border-primary border-opacity-50 d-flex justify-content-between align-content-center">
-        <span class="fs-4 fs-bold text-primary">{{ proceedings.preface_title }}</span>       <span class="text-muted">(click to expand/contract)</span>
+        <span class="fs-4 fs-bold text-primary">{{ proceedings.preface_title }}</span>
+        <span class="text-muted">(click to expand/collapse)</span>
       </div>
       <p class="details-preview p-2 mb-0">{{ proceedings.preface_text|safe|truncatewords_html:60 }}</p>
     </summary>