This config was removed so remove all references to it.

Fixes: f7e33bdb ("fs: remove mandatory file locking support")
Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>