Bug#872322: don't mention ipheth-dkms in README anymore

[積丹尼 Dan Jacobson]

Package: ipheth-utils
Version: 1.0-3+b4
Severity: wishlist
File: /usr/share/doc/ipheth-utils/README.Debian

/usr/share/doc/ipheth-utils/NEWS.Debian.gz says ipheth-dkms has already
been removed, so perhaps don't mention it anymore in README.Debian.