[gnome-builder/wip/gtk4-port] libide/greeter: use flat property instead of css-class

[Christian Hergert <chergert src gnome org>]

commit 44f414e7c4c562d5dd9d2ed577974dfedf3dc30c
Author: Christian Hergert <chergert redhat com>
Date:   Mon May 16 12:19:53 2022 -0700

    libide/greeter: use flat property instead of css-class

 src/libide/greeter/ide-greeter-workspace.ui | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)
---
diff --git a/src/libide/greeter/ide-greeter-workspace.ui b/src/libide/greeter/ide-greeter-workspace.ui
index 90ba106fb..959896ac9 100644
--- a/src/libide/greeter/ide-greeter-workspace.ui
+++ b/src/libide/greeter/ide-greeter-workspace.ui
@@ -4,12 +4,10 @@
   <template class="IdeGreeterWorkspace" parent="IdeWorkspace">
     <child type="titlebar">
       <object class="IdeHeaderBar" id="header_bar">
+        <property name="flat">true</property>
         <property name="menu-id">ide-greeter-workspace-menu</property>
         <child internal-child="headerbar">
           <object class="AdwHeaderBar">
-            <style>
-              <class name="flat"/>
-            </style>
           </object>
         </child>
         <child type="title">