When tape this line and restart the service apache2 nothing changes
Apache in any way does not related to handling svn:// protocol
Quote from referenced by you page of SVN Book
Once we successfully start svnserve as explained previously, it makes every repository on your system available to the network. A client needs to specify an absolute path in the repository URL. For example, if a repository is located at /var/svn/project1, a client would reach it via svn://host.example.com/var/svn/project1.
(Bolded parts is important)