"The z_tilt_adjust was coded to require 3 points because the original
intent was for railcore-xl and voron. Since then, a number of users
have started using z_tilt_adjust for prusa i3 style printers with dual z
steppers. That's fine, but we just haven't gotten around to removing
the superfluous check in the code." -- Kevin O'Connor
remove that check.
Signed-off-by: John "Fess" Fessenden <fess@fess.org>