[gnome-control-center] printers: Apply the vertical spacing standard

[Felipe Borges <felipeborges src gnome org>]

commit c776ab180832d938b8117b81254fcb0ce7847cf5
Author: Felipe Borges <felipeborges gnome org>
Date:   Thu Aug 24 12:46:39 2017 +0200

    printers: Apply the vertical spacing standard
    
    Settings panels are given 32px above and below their content
    and 32px vertical space between major sections. 12px space is
    placed below headings.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=786384

 panels/printers/printers.ui |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/panels/printers/printers.ui b/panels/printers/printers.ui
index 376c3f1..248f846 100644
--- a/panels/printers/printers.ui
+++ b/panels/printers/printers.ui
@@ -139,6 +139,8 @@
                     <property name="visible">True</property>
                     <property name="can_focus">True</property>
                     <property name="selection-mode">GTK_SELECTION_NONE</property>
+                    <property name="margin-top">32</property>
+                    <property name="margin-bottom">32</property>
                     <style>
                       <class name="background"/>
                     </style>