tty: Fix typo in LEGACY_TIOCSTI Kconfig description

Fix typo in LEGACY_TIOCSTI Kconfig description

There is a stray ' in the description before the Y. It appears this was
meant as a quote for the 'Y'. However, it is more common to use
unquoted Y in Kconfig descriptions.

Signed-off-by: Hanno Böck <hanno@hboeck.de>
Link: https://lore.kernel.org/r/20230330213557.60cf1533.hanno@hboeck.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>