I associated a groupwanted expression with a group I called "common", but I don't want it any more. Can I remove it, so the group doesn't have any groupwanted expression?

I tried to remove it with git annex groupwanted common '', but when I run git annex vicfg, I just end up with groupwanted common =. Similarly, if I run git annex vicfg and delete that line, it seems to have no effect.

I'm assuming (but haven't verified) that means I won't be able to use groupwanted properly with repos that are in common and also in a group that has a real expression associated with it.

How can I make it so common no longer has an associated expression?