jack: Fix removing of examples tools and manpages

pkgsrc changes:
---------------
  * The main part of binaries provided by this package are example tools.
    The 1.9.21 seems to be the last release where these tools are included
    in this the repository of jack. There is now a dedicated repository for
    these tools: https://github.com/jackaudio/jack-example-tools.
    We should plan to add audio/jack-example-tools to package this tools in
    a near future.
  * The man pages are surprisingly conditioned by the --example-tools
    option.
  * Bump revision.

(triaxx)