[gnome-shell] build: Bump mutter API version

[Florian Müllner <fmuellner src gnome org>]

commit ea0770ae22a6c34797db4343cf7d2f59bb8d68f6
Author: Jonas Ådahl <jadahl gmail com>
Date:   Wed Feb 21 23:43:18 2018 +0800

    build: Bump mutter API version
    
    The API number was updated, let's keep up.

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index 14b99bf60..d24b9ada4 100644
--- a/meson.build
+++ b/meson.build
@@ -6,7 +6,7 @@ project('gnome-shell', 'c',
 
 # We depend on a specific version of the libmutter API. The mutter variants of
 # the Cogl and Clutter libraries also use this API version.
-mutter_api_version = '1'
+mutter_api_version = '2'
 
 clutter_pc = 'mutter-clutter-' + mutter_api_version
 cogl_pc = 'mutter-cogl-' + mutter_api_version