In my experience with this infection the malicious code is probably going to be at the very, very bottom of one of these two files:
./wp-content/twentyeleven/footer.php
./wp-content/twentyeleven/index.php
You can remove that malicious script from there and that should clear the Sucuri Sitecheck warning, but the challenge will be determining if the attacker placed any back doors in order to reinfect the site at a later date.
You might want to run a file integrity check as well as a general scan of your files with a security plugin to see if any other malicious scripts are present there.