Update CHANGELOG.md to reflect the promotion of 15.1.5
Update CHANGELOG.md to reflect the promotion of 15.1.5

Obvious fix; these changes are the result of automation not creative thinking.

chef/ohai,jaymzh/ohai,mattray/ohai,jaymzh/ohai,higanworks/ohai,higanworks/ohai,chef/ohai,mattray/ohai