snapshot: Make gtk_snapshot_get_renderer() private

Public API doesn't need to be concerned with renderers. Worst case, they
can use NULL instead of the actual renderer.

docs/reference/gtk/gtk4-sections.txt

@@ -4453,7 +4453,6 @@ gtk_volume_button_get_type
 <FILE>gtksnapshot</FILE>
 <TITLE>GtkSnapshot</TITLE>
 GtkSnapshot
-gtk_snapshot_get_renderer
 gtk_snapshot_push
 gtk_snapshot_push_node
 gtk_snapshot_pop

gtk/gtkiconhelper.c

@@ -553,8 +553,7 @@ gtk_icon_helper_ensure_surface (GtkIconHelper *self)
 }
 
 static void
-gtk_icon_helper_ensure_texture (GtkIconHelper *self,
-                                GskRenderer   *renderer)
+gtk_icon_helper_ensure_texture (GtkIconHelper *self)
 {
   cairo_surface_t *map;
   int width, height, scale;
@@ -874,7 +873,7 @@ gtk_icon_helper_snapshot (GtkIconHelper *self,
   GtkCssStyle *style;
   GskTexture *texture;
 
-  gtk_icon_helper_ensure_texture (self, gtk_snapshot_get_renderer (snapshot));
+  gtk_icon_helper_ensure_texture (self);
   texture = self->priv->texture;
   if (texture == NULL)
     return;

gtk/gtksnapshot.h

@@ -36,9 +36,6 @@
 
 G_BEGIN_DECLS
 
-GDK_AVAILABLE_IN_3_90
-GskRenderer *   gtk_snapshot_get_renderer               (const GtkSnapshot      *snapshot);
-
 GDK_AVAILABLE_IN_3_90
 void            gtk_snapshot_push                       (GtkSnapshot            *snapshot,
                                                          gboolean                keep_coordinates,

gtk/gtksnapshotprivate.h

@@ -48,6 +48,8 @@ void            gtk_snapshot_init               (GtkSnapshot             *state,
                                                  ...) G_GNUC_PRINTF (4, 5);
 GskRenderNode * gtk_snapshot_finish             (GtkSnapshot             *state);
 
+GskRenderer *   gtk_snapshot_get_renderer       (const GtkSnapshot       *snapshot);
+
 G_END_DECLS
 
 #endif /* __GTK_SNAPSHOT_PRIVATE_H__ */