[pan] configure.ac: required Gtk2 version is 2.24.0

[Dominique Dumont <ddumont src gnome org>]

commit ca1f30712b34c2c8315e3a3d754adc09a4dcdba9
Author: Dominique Dumont <dod debian org>
Date:   Sat Jun 25 17:03:41 2022 +0200

    configure.ac: required Gtk2 version is 2.24.0

 configure.ac | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/configure.ac b/configure.ac
index fa0b404..aaaacff 100644
--- a/configure.ac
+++ b/configure.ac
@@ -51,7 +51,7 @@ dnl glib, gmime, and gtk are mandatory prerequisites.
 GLIB_REQUIRED=2.17.6
 GLIB_REQUIRED_FOR_DBUS=2.26.0
 GMIME30_REQUIRED=3.0.0
-GTK_REQUIRED=2.16.0
+GTK_REQUIRED=2.24.0
 GTK3_REQUIRED=3.0.0
 GTKSPELL_REQUIRED=2.0.7
 GTKSPELL3_REQUIRED=2.0.16