man page says, under the SCRIPTS OF INTEREST section:
When an automatic reboot is in progress, rc is invoked with the argument
autoboot. One of the scripts run from /etc/rc.d/ is /etc/rc.d/fsck.
This script runs fsck(8) with option -p and -F to ``preen'' all the disks
of minor inconsistencies resulting from the last system shutdown. If
this fails, then checks/repairs of serious inconsistencies caused by
hardware or software failure will be performed in the background at the
end of the booting process. If autoboot is not set, when going from sin-
gle-user to multi-user mode for example, the script does not do anything.
Now that you know what you can edit to prevent fsck from running, I recommend strongly that you DON'T DO IT. If there are filesystem inconsistencies, and you change anything in the filesystem, you risk altering the integrity of the filesystem and losing part or all of it.
Mount inconsistent filesystems read-only, if you must access data quickly and you cannot wait for fsck to complete its work. Writing on them in that state would be a poor operational decision.