[gtksourceview] test-widget: add some margin

[Christian Hergert <chergert src gnome org>]

commit 2960ee00abc19d843b0dd4435258c9826050cefb
Author: Christian Hergert <chergert redhat com>
Date:   Mon Aug 9 11:21:11 2021 -0700

    test-widget: add some margin
    
    To test margin propagation to right.

 tests/test-widget.ui | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/tests/test-widget.ui b/tests/test-widget.ui
index f3e2ca9c..496684fe 100644
--- a/tests/test-widget.ui
+++ b/tests/test-widget.ui
@@ -460,6 +460,7 @@
         </child>
         <child>
           <object class="GtkSourceMap" id="map">
+            <property name="left-margin">12</property>
             <property name="visible">True</property>
             <property name="can_focus">False</property>
             <property name="view">view</property>