grub2: remove package

Grub 2 has been marked BROKEN in June 2010, and nobody cared to fix it
since then.

At that time, it was marked broken because the build process needed a
Ruby interpreter available on the host, and it's really a pain that
building a bootloader needs such a thing.

I've tried to upgrade the package to Grub2 1.99-rcX, and now it does
not need a Ruby interpreter anymore, but instead requires a tool
called "autogen", which itself needs the Guile Scheme interpreter.

Since we haven't heard any complaints about Grub2 being marked broken,
and since it's such a pain to package, let's get rid of it. Of course,
anybody interested in Grub2 is invited to contribute a working
package.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>