Fix the RFC number mentioned when complaining about a missing

Host: header.

PR:             7079
Submitted by:   Alexey Toptygin <alexeyt@wam.umd.edu>


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@87717 13f79535-47bb-0310-9956-ffa450edef68