docs: Kinematics.md updates for extruder instantaneous corner velocity

As of commit 5f5896a Klipper will perform look-ahead between moves
even if they have significant differences in extruder flow rates.
Update Kinematics.md accordingly.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

docs/Kinematics.md

@@ -92,10 +92,6 @@ desired speed that a 90° corner should have (the "square corner
 velocity"), and the junction speeds for other angles are derived from
 that.
 
-Klipper implements look-ahead between moves that have similar extruder
-flow rates. Other moves are relatively rare and implementing
-look-ahead between them is unnecessary.
-
 Key formula for look-ahead:
 ```
 end_velocity^2 = start_velocity^2 + 2*accel*move_distance