Make the Appledoc build again

Appledoc no longer accepts the docsetutil-path flag (https://github.com/tomaz/appledoc/issues/257). Taking it out of the build script let made the documentation build succeed for me. I'm not sure which Xcode/Appledoc version pairs still need this flag; at some point, however, it's no longer going to make sense to have this flag in the script by default.