Documentation: update stable review cycle documentation

Documentation: update stable review cycle documentation

In recent times, the review cycle for stable releases have been changed.
In particular, there is release candidate phase between ACKing patches
and new stable release. Also, in case of failed submissions (fail to
apply to stable tree), manual backport (Option 3) have to be submitted
instead.

Update the release cycle documentation on stable-kernel-rules.rst to
reflect the above.

Cc: Sasha Levin <sashal@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://lore.kernel.org/r/20220314113329.485372-4-bagasdotme@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>