Drop memtest86+ from Fedora 35+ (#1988142)
    
    It doesn't work - see also devel@ thread "replace memtest86+ with
    pcmemtest, needs maintainer". Until we sort out pcmemtest or some
    other replacement, let's just get rid of it. The image creation
    tools should smoothly omit the menu entry at creation time if
    the package is not there.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>