docs: networking: bonding.rst resources section cleanup

Removed obsolete resources from bonding.rst doc:
   - bonding-devel@lists.sourceforge.net hasn't been used since 2008
   - admin interface is 404
   - Donald Becker's domain/content no longer online

Signed-off-by: Nivedita Singhvi <nivedita.singhvi@canonical.com>
Acked-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>