Stop using GtkWidget:margin

GTK4 removes it and leaves margin-top etc. Use them directly.

Part-of: <!1038>

lib/ephy-notification.c

@@ -146,10 +146,11 @@ ephy_notification_init (EphyNotification *self)
   gtk_grid_attach (GTK_GRID (self->grid), self->body, 0, 1, 1, 1);
 
   self->close_button = gtk_button_new ();
-  g_object_set (self->close_button,
-                "focus-on-click", FALSE,
-                "margin", 6,
-                NULL);
+  gtk_widget_set_focus_on_click (self->close_button, FALSE);
+  gtk_widget_set_margin_top (self->close_button, 6);
+  gtk_widget_set_margin_bottom (self->close_button, 6);
+  gtk_widget_set_margin_start (self->close_button, 6);
+  gtk_widget_set_margin_end (self->close_button, 6);
   gtk_style_context_add_class (gtk_widget_get_style_context (self->close_button), "flat");
   gtk_grid_attach (GTK_GRID (self->grid), self->close_button, 1, 0, 1, 2);
 

lib/widgets/ephy-security-popover.c

@@ -534,7 +534,10 @@ ephy_security_popover_init (EphySecurityPopover *popover)
   popover->grid = gtk_grid_new ();
   gtk_grid_set_column_spacing (GTK_GRID (popover->grid), 12);
   gtk_grid_set_row_spacing (GTK_GRID (popover->grid), 6);
-  g_object_set (popover->grid, "margin", 10, NULL);
+  gtk_widget_set_margin_top (popover->grid, 10);
+  gtk_widget_set_margin_bottom (popover->grid, 10);
+  gtk_widget_set_margin_start (popover->grid, 10);
+  gtk_widget_set_margin_end (popover->grid, 10);
 
   box = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 6);
   gtk_widget_set_halign (box, GTK_ALIGN_CENTER);

src/resources/gtk/webapp-additional-urls-dialog.ui

@@ -21,7 +21,10 @@
           <object class="GtkLabel">
             <property name="visible">True</property>
             <property name="xalign">0</property>
-            <property name="margin">12</property>
+            <property name="margin-top">12</property>
+            <property name="margin-bottom">12</property>
+            <property name="margin-start">12</property>
+            <property name="margin-end">12</property>
             <property name="label" translatable="yes">A URL that starts with any of the additional URLs will be opened by the web application. If you omit the URL scheme, the one from the currently loaded URL will be used.</property>
             <property name="wrap">True</property>
           </object>