Merge branch Mario/speed_powerup_noeffects (XXS merge request)

Disables the bubbly particles that show while holding the Speed powerup, as the effect is too subtle to notice while being a distraction in first person view.
No effect is in place as a replacement yet, as it is not really needed; players who hold this will already be visually indicated by their speed, as opposed to the other powerups which apply flat buffs and can be considerably more dangerous if unnoticed.

Closes #2668 (closed)