c-e: fix ce-ppp-auth-methods.ui as well

Fix ce-ppp-auth-methods.ui as well per Mikhail's comment

!75 (comment 685501)

Fixes: 5fbf69f2 ('glade: get rid of GtkContainer.border-width')

src/connection-editor/ce-ppp-auth-methods.ui

@@ -4,10 +4,6 @@
   <requires lib="gtk+" version="3.10"/>
   <object class="GtkDialog" id="auth_methods_dialog">
     <property name="can_focus">False</property>
-    <property name="margin_start">5</property>
-    <property name="margin_end">5</property>
-    <property name="margin_top">5</property>
-    <property name="margin_bottom">5</property>
     <property name="window_position">center-on-parent</property>
     <property name="default_width">400</property>
     <property name="icon_name">stock-preferences</property>
@@ -17,6 +13,10 @@
         <property name="visible">True</property>
         <property name="can_focus">False</property>
         <property name="orientation">vertical</property>
+        <property name="margin_start">5</property>
+        <property name="margin_end">5</property>
+        <property name="margin_top">5</property>
+        <property name="margin_bottom">5</property>
         <property name="spacing">2</property>
         <child internal-child="action_area">
           <object class="GtkButtonBox" id="dialog-action_area1">