Remove a compatibility note that is not relevant any more.

The corresponding code was added in r1807709 but reverted in r1827760.
The compatibility note was added as part of r1807869 but was not removed when the code has been axed.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1834220 13f79535-47bb-0310-9956-ffa450edef68