(#16347) Replace \x92 character with apostrophe

Previously, there was a non-ascii character in the comment, which caused
a warning when building rdoc during gem install puppet on ruby 1.9.3.
It is possible from a copy & paste from MS Word smart apostrophe.

This commit doesn't change any code, just the comment.

Paired-with: Andy Parker <andy@puppetlabs.com>