[gnome-calendar] Bump 3.31.0 release

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 12866fc74149b434d597d9b91dfb6393caf16335
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Sat Sep 15 01:52:34 2018 -0300

    Bump 3.31.0 release

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index c7de271a..09514271 100644
--- a/meson.build
+++ b/meson.build
@@ -1,7 +1,7 @@
 project(
   'gnome-calendar',
                'c',
-           version: '3.30.0',
+           version: '3.31.0',
            license: 'GPL3+',
      meson_version: '>= 0.42.0'
 )