[nautilus] configure: bump gtk version requirement

[Michael Biebl <mbiebl src gnome org>]

commit cbdaccf8be20ad9d3eff69b613ac895525474aff
Author: Michael Biebl <biebl debian org>
Date:   Wed Sep 14 04:15:11 2016 +0200

    configure: bump gtk version requirement
    
    We need at least 3.21.6 for GtkScrolledWindow.propagate-natural-height
    since 2f878b79c43676eef37e00a1e1d4b1572d2cf341

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 0af3618..3da0172 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5,7 +5,7 @@ dnl ===========================================================================
 m4_define(glib_minver,                 2.49.1)
 m4_define(gnome_desktop_minver,        3.0.0)
 m4_define(pango_minver,                1.28.3)
-m4_define(gtk_minver,                  3.21.5)
+m4_define(gtk_minver,                  3.21.6)
 m4_define(xml_minver,                  2.7.8)
 m4_define(exif_minver,                 0.6.20)
 m4_define(exempi_minver,               2.1.0)