Increase projectile speed slightly across the board.
This bumps arrows from 75 to 100, slingers to 90 and javelins from 62.5 to 70. It's both slightly more realistic and helps with dancing, since the problem is the ratio of unit speed vs projectile speed.
Further increases would reduce dancing, but also make it harder to see projectiles which isn't desirable.
Differential Revision: https://code.wildfiregames.com/D3179