Remove the general not-updated warning for perf-tuning,

Remove the general not-updated warning for perf-tuning,
since the document is mostly accurate.  But since the
accept-mutex section seems a little dated, leave a
warning there.  That could use some developer intervention.

Also, remove the author attribution, since large parts
of this have changed since Dean wrote it.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@100899 13f79535-47bb-0310-9956-ffa450edef68