[libshumate/tintou/style-class] scale: Use hardcoded string for style class

[Corentin Noël <corentinnoel src gnome org>]

commit 8e1eee83b707d520d7e38d708fede66402b23f1f
Author: Corentin Noël <corentin noel collabora com>
Date:   Tue Sep 22 11:39:20 2020 +0200

    scale: Use hardcoded string for style class
    
    The constants for style classes have been removed from GTK itself.

 shumate/shumate-scale.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/shumate/shumate-scale.c b/shumate/shumate-scale.c
index 30e53b8..26bc36e 100644
--- a/shumate/shumate-scale.c
+++ b/shumate/shumate-scale.c
@@ -376,7 +376,7 @@ shumate_scale_init (ShumateScale *self)
   self->max_scale_width = 150;
 
   gtk_orientable_set_orientation (GTK_ORIENTABLE (layout), GTK_ORIENTATION_VERTICAL);
-  gtk_widget_add_css_class (self_widget, GTK_STYLE_CLASS_VERTICAL);
+  gtk_widget_add_css_class (self_widget, "vertical");
 
   self->metric_label = gtk_label_new (NULL);
   g_object_set (G_OBJECT (self->metric_label),