[mutter] Post-release version bump

[Florian Müllner <fmuellner src gnome org>]

commit c5ad7fe2b402f1540173bc67430bc0e934725bbd
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Dec 2 20:38:43 2020 +0100

    Post-release version bump

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index a969667bf2..782a8e3640 100644
--- a/meson.build
+++ b/meson.build
@@ -1,5 +1,5 @@
 project('mutter', 'c',
-  version: '40.alpha',
+  version: '40.beta',
   meson_version: '>= 0.51.0',
   license: 'GPLv2+'
 )