Fix documentation of ProxyPass/ProxyPassReverse according to the

trailing slash problem.

Submitted by: Jon Drukman <jsd@gamespot.com>
Reviewed by: Ralf S. Engelschall
PR: 2933


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@82023 13f79535-47bb-0310-9956-ffa450edef68