Backport 1825368:

rpm: Remove rpm build for mod_socache_dc, the dependency distcache has long since
stopped being available in RPM distros.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1825369 13f79535-47bb-0310-9956-ffa450edef68