[gdm] meson: Fix version to be 40.0 not 40

[Ray Strode <halfline src gnome org>]

commit 3246bf1af8589899621649df523e6840e4858cda
Author: Ray Strode <rstrode redhat com>
Date:   Tue Mar 30 09:25:17 2021 -0400

    meson: Fix version to be 40.0 not 40

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index cd1101219..e6fcf4b8b 100644
--- a/meson.build
+++ b/meson.build
@@ -1,5 +1,5 @@
 project('gdm', 'c',
-  version: '40',
+  version: '40.0',
   license: 'GPL2+',
   meson_version: '>= 0.50',
 )