Fix issue 2162 - Remove doc references to svn:this_dir
Fix issue 2162 - Remove doc references to svn:this_dir

* doc/book/book/ch08.xml (svn-ch-8-sect-3-ex-1): WC entries files have not used
    "svn:this_dir" for the directory's name for a long time now. Correct this.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion