docs: fix typo in table describing 4.16 development cycle

Fix s/4.17/4.16/ typo.

Fixes: 8962e40c ("docs: update kernel versions and dates in tables")
Cc: Tim Bird <tim.bird@sony.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>