CTR: docs
Remove obsolete documentation from realm package javadoc.
The text is something very old that talks about "debug" attribute and that there are two standard realms, JDBCRealm and MemoryRealm.
The up-to-date documentation is maintained in docs/config/realm.html
Merged r1601856 from tomcat/tc7.0.x/trunk.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc6.0.x/trunk@1601857 13f79535-47bb-0310-9956-ffa450edef68