Reduced speed while auto-crouching affects players in spectator mode

The speed limiting applied to the fix of MC-147270 affects players in spectator mode.

Steps to reproduce

1. Change to spectator mode.
2. Go under a 1.5 or less blocks height space.
3. Press crouch, which is the key to decrease fly height.
4. You will be affected by the speed limiter while clipping through blocks. Speed will be back to normal once you're back in open space.