Remove stale branches

[raimue]

Remove stale branches for www and guide.

[neverpanic]

I would have removed all stale branches after conversion, t.b.h.

Removing them like this will cause warnings to be emitted. I was discussing with @ryandesign whether we should be adding rules to explicitly silence these warnings to mark that we're ignoring them on purpose, e.g.

match /branches/jkh-destrootification/www/
    # ignored on purpose
end match

[raimue]

I am also fine with deleting them after the conversion, it just needs to be done at some point.