Use Unicode in translatable strings

See https://developer.gnome.org/hig/stable/typography.html

https://bugzilla.gnome.org/show_bug.cgi?id=772221

gio/gicon.c

@@ -458,7 +458,7 @@ g_icon_new_for_string (const gchar   *str,
     g_set_error_literal (error,
                          G_IO_ERROR,
                          G_IO_ERROR_INVALID_ARGUMENT,
-                         _("Can't handle the supplied version of the icon encoding"));
+                         _("Can’t handle the supplied version of the icon encoding"));
 
   return icon;
 }