[four-in-a-row] prefs-box: Fix a typo in a user-visible string

[Piotr Drąg <piotrdrag src gnome org>]

commit 16e8c6f801090cf8347ebfc8d8480f10bf08785f
Author: Piotr Drąg <piotrdrag gmail com>
Date:   Mon Dec 17 21:06:00 2018 +0100

    prefs-box: Fix a typo in a user-visible string

 src/prefs-box.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/prefs-box.vala b/src/prefs-box.vala
index 83c3407..98ecf9c 100644
--- a/src/prefs-box.vala
+++ b/src/prefs-box.vala
@@ -76,7 +76,7 @@ class PrefsBox : Gtk.Dialog {
         if (Prefs.instance.level[PlayerID.PLAYER2] == Level.MEDIUM)
             combobox.set_active_iter(iter);
         model.append(out iter);
-        model.set(iter, 0, _("Level thre"), 1, Level.STRONG);
+        model.set(iter, 0, _("Level three"), 1, Level.STRONG);
         if (Prefs.instance.level[PlayerID.PLAYER2] == Level.STRONG)
             combobox.set_active_iter(iter);