Fix typo in comment (s/patterm/pattern/).

Backport of r1726086 from trunk
resp. r1726087 from 2.4.x.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1726089 13f79535-47bb-0310-9956-ffa450edef68