[gnome-documents] build: Bump minimum GTK+ version to 3.22.15

[Debarshi Ray <debarshir src gnome org>]

commit 26c1cb6641921d1a5001d3c3479d98053e5fecc8
Author: Debarshi Ray <debarshir gnome org>
Date:   Wed Jun 21 14:09:30 2017 +0200

    build: Bump minimum GTK+ version to 3.22.15
    
    We need it for the new entry-tag CSS style class that we rely on since
    commit 5c0eeec06920ce50d9678d5586487a347cfe39b9

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 2a05eac..8a30d35 100644
--- a/configure.ac
+++ b/configure.ac
@@ -53,7 +53,7 @@ EVINCE_MIN_VERSION=3.13.3
 WEBKITGTK_MIN_VERSION=2.6.0
 GLIB_MIN_VERSION=2.39.3
 GJS_MIN_VERSION=1.48.0
-GTK_MIN_VERSION=3.22.10
+GTK_MIN_VERSION=3.22.15
 GOBJECT_INTROSPECTION_MIN_VERSION=1.31.6
 TRACKER_MIN_VERSION=0.17.3
 SOUP_MIN_VERSION=2.41.3