meson.build: Increase meson version

This fixes WARNING: Project specifies a minimum meson_version '>= 0.56.2'
but uses features which were added in newer versions:
 * 0.58.0: {'str.replace'}

meson.build

@@ -2,7 +2,7 @@ project(
   'xdg-desktop-portal',
   'c',
   version: '1.18.1',
-  meson_version: '>= 0.56.2',
+  meson_version: '>= 0.58',
   license: 'LGPL-2.0-or-later',
   default_options: ['warning_level=2'])