[sound-juicer] Require Gtk 3.21.6

[Phillip Wood <pwood src gnome org>]

commit c46d5d44899c309e892f59ab6dd6297478bdb4a0
Author: Phillip Wood <phillip wood dunelm org uk>
Date:   Mon Sep 19 12:59:51 2016 +0100

    Require Gtk 3.21.6
    
    This version provides GtkScrolledWindow:propagate-natural-height/width.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 6ba8fe5..e081b4f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -30,7 +30,7 @@ AC_PROG_MKDIR_P
 
 GNOME_COMPILE_WARNINGS([maximum])
 
-GTK_REQUIRED=3.21.3
+GTK_REQUIRED=3.21.6
 GLIB_GSETTINGS
 
 # Find glib-compile-resources