[fractal] join_room: Clean up child props and placeholders

[Daniel Garcia Moreno <danigm src gnome org>]

commit 9a81e50a490d9fe11938194871069eb17e2aa307
Author: Christopher Davis <brainblasted disroot org>
Date:   Sat Oct 31 16:02:01 2020 -0700

    join_room: Clean up child props and placeholders
    
    Placeholders aren't needed, and child properties
    are gone in GTK4

 fractal-gtk/res/ui/join_room.ui | 23 -----------------------
 1 file changed, 23 deletions(-)
---
diff --git a/fractal-gtk/res/ui/join_room.ui b/fractal-gtk/res/ui/join_room.ui
index a04a0f12..72838857 100644
--- a/fractal-gtk/res/ui/join_room.ui
+++ b/fractal-gtk/res/ui/join_room.ui
@@ -16,24 +16,6 @@
       <object class="GtkBox">
         <property name="can_focus">False</property>
         <property name="orientation">vertical</property>
-        <property name="spacing">2</property>
-        <child internal-child="action_area">
-          <object class="GtkButtonBox">
-            <property name="can_focus">False</property>
-            <property name="layout_style">end</property>
-            <child>
-              <placeholder/>
-            </child>
-            <child>
-              <placeholder/>
-            </child>
-          </object>
-          <packing>
-            <property name="expand">False</property>
-            <property name="fill">False</property>
-            <property name="position">0</property>
-          </packing>
-        </child>
         <child>
           <object class="GtkGrid">
             <property name="visible">True</property>
@@ -75,11 +57,6 @@
               </packing>
             </child>
           </object>
-          <packing>
-            <property name="expand">False</property>
-            <property name="fill">True</property>
-            <property name="position">1</property>
-          </packing>
         </child>
       </object>
     </child>