Fix dead link to Apple's whitepaper on their AutoFS implementation using Archive.org mirror.
Reword sentence leading up to link with a friendlier toned version.
Replace contractions & spelling mistake raised by Igor.

PR: 213022
Reported by: Ranjit Marathay <rmarathay at gmail dot com>
Approved by: bcr (mentor) wblock
Differential Revision: https://reviews.freebsd.org/D8156