A follow-up to r24211, clarifying a description.
A follow-up to r24211, clarifying a description.

* www/roadmap.html
  Clarify description of sparse checkouts.

Suggested by: lundblad

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