[gnome-screenshot] build: use meson 0.50.0

[Cosimo Cecchi <cosimoc src gnome org>]

commit a5a2bbbbe0a37177b414677f0419bc88fe98e435
Author: Cosimo Cecchi <cosimoc gnome org>
Date:   Tue Aug 6 11:39:12 2019 +0200

    build: use meson 0.50.0

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index d541dd1..a05c048 100644
--- a/meson.build
+++ b/meson.build
@@ -1,7 +1,7 @@
 project('gnome-screenshot', 'c',
         version: '3.32.0',
         license: 'GPLv2+',
-        meson_version: '>= 0.40.1',
+        meson_version: '>= 0.50.0',
         default_options: [
           'buildtype=debugoptimized',
           'warning_level=1',