mod_authn_file, mod_authz_groupfile: remove an unused and undocumented

"standard" optional parameter for 'AuthGroupFile' and 'AuthUserFile'

trunk patch: http://svn.apache.org/r1484398
Submitted by: jailletc36
Reviewed by: covener, minfrin


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1485737 13f79535-47bb-0310-9956-ffa450edef68