Update release cadence documentation
Signed-off-by:Felix Thomasmathibalan <felixjohnny.thomasmathibalan@arm.com> Approved-by:
Viet-Hoa Do <viet-hoa.do@arm.com>
Signed-off-by:Felix Thomasmathibalan <felixjohnny.thomasmathibalan@arm.com> Approved-by:
Viet-Hoa Do <viet-hoa.do@arm.com>