Yes, edit the /skins/leaf/_main.php file and remove the section in the sidebar that creates the stats. Then remove the /skins/leaf/_stats.php file.

AND upgrade your blog!!!

"Recent referers" hasn't been part of the distribution since 0.9.1 but you should upgrade to 0.9.2 as it is the highest release you can upgrade to without too much work to retain your skin and your hacks. In addition to not showing stats publicly there are a bunch of other improvements including my favorite: it reduces the load on your server by a gazillion percent because of how .9.1 and .9.2 shut out spammers immediately.

Yes, upgrading is a good idea, but if you keep the skin you're using now it will still show referral stats even after upgrading. So, upgrade AND edit the skin.