appdb new version submission form has awkward radio buttons

[Dan Kegel]

When submitting a new version, clicking the radio button next
to "Request being a maintainer for this version, allowing you to edit it later"
or "Monitor changes to this version, also after it has been accepted"
can't be undone.  There should be a way to get back to the state
of no button clicked.  Perhaps those should be checkboxes instead.