[libpeas] libpeas-gtk: remove deprecated use of gtk_show_uri_on_window()

[Christian Hergert <chergert src gnome org>]

commit 616d74287fbf54c9e5c75a381ce34d25aa21eb4f
Author: Christian Hergert <chergert redhat com>
Date:   Mon Aug 5 14:51:38 2019 -0700

    libpeas-gtk: remove deprecated use of gtk_show_uri_on_window()
    
    This is fairly trivial to switch to the non-deprecated API.

 libpeas-gtk/peas-gtk-plugin-manager.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/libpeas-gtk/peas-gtk-plugin-manager.c b/libpeas-gtk/peas-gtk-plugin-manager.c
index fc2508a..2198a4f 100644
--- a/libpeas-gtk/peas-gtk-plugin-manager.c
+++ b/libpeas-gtk/peas-gtk-plugin-manager.c
@@ -193,7 +193,7 @@ help_button_cb (GtkWidget      *button,
   [[NSWorkspace sharedWorkspace] openURL:[NSURL URLWithString:[NSString stringWithUTF8String:help_uri]]];
 #else
 
-  gtk_show_uri (NULL, help_uri, GDK_CURRENT_TIME, &error);
+  gtk_show_uri_on_window (get_toplevel (button), help_uri, GDK_CURRENT_TIME, &error);
   if (error == NULL)
     return;