Fix activity feed pagination to fetch on demand

Commit 01c642e6 restructured the page so that the "next page" link was
always in view, meaning the page always loaded the entire history.

Now we load the next day as the user scrolls to the bottom, as intended.

app/views/events/index.html.erb

@@ -36,5 +36,5 @@
 </header>
 <div class="events" id="activity">
   <%= render "events/day", day_timeline: @day_timeline %>
-  <%= event_next_page_link(@day_timeline.next_day) %>
 </div>
+<%= event_next_page_link(@day_timeline.next_day) %>