I'm wondering what the easiest way for me to delete the following lines from my /etc/crontab file would be?

*/5 21-23 * * 5,6 root renice -20 \`cat /usr/games/hlds_l/hlds.pid\` >/dev/null 2>&1
*/5 0-5 * * 0,6 root renice -20 \`cat /usr/games/hlds_l/hlds.pid\` >/dev/null 2>&1

I run game servers on weekend nights and I have a script that starts and stops the server, and I'd like the startup script to add these lines, while the shutdown script deletes them. The reason I don't just leave them in there is that I run two different game servers, hlds and srcds. I could just put lines for both of them in the crontab and leave them there, but I'd rather the commands only run if I need them.