Fix underwater strafing activating below minimum speed and pushing you backward

- Below 11 FU, strafing is not supposed to kick in
- But the order of operations looked weird, and it seems
  to have been kicking in erroneously as a result
  - This would push the player in the opposite of their
    facing angle when they tried to drive forward and turn
    at the same time
  - Strong enough offroad is required to trigger this

src/k_kart.c

@@ -10176,7 +10176,7 @@ static fixed_t K_GetUnderwaterStrafeMul(const player_t *player)
 
 	baseline = 2 * K_GetKartSpeed(player, true, true) / 3;
 
-	return max(0, FixedDiv(player->speed - minSpeed, baseline - minSpeed));
+	return max(0, FixedDiv(max(player->speed, minSpeed) - minSpeed, baseline - minSpeed));
 }
 
 INT16 K_GetKartTurnValue(const player_t *player, INT16 turnvalue)