Fix CGIPassAuth built-in directive documentation,

Get compatibility line in doc ready for backport

Pointed out by: rjung (who perhaps wasn't so positive about the eventual 2.4.x release)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1673155 13f79535-47bb-0310-9956-ffa450edef68