[gnome-games] Fix error message

[Alexander Mikhaylenko <alexm src gnome org>]

commit cbb6a2e6666a227e7b738f827debc6354acd1477
Author: Michael Scherer <misc redhat com>
Date:   Fri Apr 10 18:15:52 2020 +0200

    Fix error message

 plugins/libretro/src/libretro-plugin.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/plugins/libretro/src/libretro-plugin.vala b/plugins/libretro/src/libretro-plugin.vala
index ea84f4f4..66fd1ace 100644
--- a/plugins/libretro/src/libretro-plugin.vala
+++ b/plugins/libretro/src/libretro-plugin.vala
@@ -46,7 +46,7 @@ private class Games.LibretroPlugin : Object, Plugin {
                var path = file.get_path ();
                var core_descriptor = new Retro.CoreDescriptor (path);
                if (!core_descriptor.get_is_game ())
-                       throw new LibretroError.NOT_A_GAME ("This Libretro core descriptor doesn't isn’t a 
game: %s", uri.to_string ());
+                       throw new LibretroError.NOT_A_GAME ("This Libretro core descriptor isn’t a game: %s", 
uri.to_string ());
 
                return core_descriptor;
        }