[gnome-games] display-header-bar: Update restore button style

[Alexander Mikhaylenko <alexm src gnome org>]

commit 853d10e5acd4b9dd357c617976906fbf00525771
Author: Alexander Mikhaylenko <exalm7659 gmail com>
Date:   Sun Aug 11 04:53:41 2019 +0500

    display-header-bar: Update restore button style
    
    Sync with gtk changes.

 data/ui/display-header-bar.ui | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)
---
diff --git a/data/ui/display-header-bar.ui b/data/ui/display-header-bar.ui
index 0eb6de8b..141c9e05 100644
--- a/data/ui/display-header-bar.ui
+++ b/data/ui/display-header-bar.ui
@@ -40,13 +40,11 @@
             <property name="can_focus">False</property>
             <property name="valign">center</property>
             <property name="use-underline">True</property>
-            <property name="margin-left">5</property>
+            <property name="margin-start">7</property>
             <signal name="clicked" handler="on_restore_clicked"/>
             <style>
               <class name="image-button"/>
-            </style>
-            <style>
-              <class name="flat"/>
+              <class name="titlebutton"/>
             </style>
             <child internal-child="accessible">
               <object class="AtkObject" id="a11y-restore">