right sidebar: Move invite link below Group PMs.

It looked kinda terrible in between the two
user lists.

There is some discussion here (I have to break the
link into two lines to make gitlint happy):

https://chat.zulip.org/#narrow/stream/
    101-design/topic/user.20sidebar.20in.20left/near/697682

templates/zerver/app/right_sidebar.html

@@ -22,9 +22,6 @@
                 <ul id="user_presences" class="filters"></ul>
                 <div id="buddy_list_wrapper_padding"></div>
             </div>
-            {% if show_invites %}
-            <a id="invite-user-link" href="#invite"><i class="fa fa-plus-circle" aria-hidden="true"></i>{{ _('Invite more users') }}</a>
-            {% endif %}
         </div>
         <div id="group-pm-list">
             <div id="group-pm-header">
@@ -33,6 +30,9 @@
             <ul id="group-pms" class="filters scrolling_list">
             </ul>
         </div>
+        {% if show_invites %}
+        <a id="invite-user-link" href="#invite"><i class="fa fa-plus-circle" aria-hidden="true"></i>{{ _('Invite more users') }}</a>
+        {% endif %}
         <a id="sidebar-keyboard-shortcuts" data-overlay-trigger="keyboard-shortcuts">
             <i class="fa fa-keyboard-o fa-2x" id="keyboard-icon" data-html="true" data-toggle="tooltip" title="{{ _('Keyboard shortcuts') }} <span class='hotkey-hint'>(?)</span>"></i>
         </a>