feeds.conf.default: remove the commented ancient feeds

Cleanup feeds.conf.default by removing the old commented-out feeds:
* x-wrt has not been updated for years and targets WhiteRussian/Kamikaze.
  No currect code base available anywhere
* six old feeds from svn.openwrt.org/feeds. These feeds have not been
  updated for 4-5 years and their code is currently unavailable
  (in svn.openwrt.org)

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

SVN-Revision: 49206