container-toolbox: Use default-editor, not nano-default-editor
    
    In Fedora 33, nano-default-editor was introduced to make GNU nano the
    default editor [1].  After a year, it was found out that it breaks
    upgrades across Fedora releases if the user had chosen some other editor
    as the default [2].
    
    The difference doesn't matter here because the fedora-toolbox OCI image
    is being created from scratch without involving any upgrades.  However,
    since fedora-comps was switched to default-editor [3], it's better to
    do the same and stay consistent.  If nothing else, it won't make the
    reader stop and ponder if there's any real reason that it was done
    differently for the fedora-toolbox image.
    
    [1] fedora nano commit cf1ce689f154d0a1
        https://src.fedoraproject.org/rpms/nano/c/cf1ce689f154d0a1
        https://src.fedoraproject.org/rpms/nano/pull-request/1
        https://fedoraproject.org/wiki/Changes/UseNanoByDefault
    
    [2] fedora nano commit e53ee57baa33a1d8
        https://src.fedoraproject.org/rpms/nano/c/e53ee57baa33a1d8
        https://src.fedoraproject.org/rpms/nano/pull-request/7
        https://bugzilla.redhat.com/show_bug.cgi?id=1955884
    
    [3] fedora-comps commit 3496ed634cf452da
        https://pagure.io/fedora-comps/c/3496ed634cf452da
        https://pagure.io/fedora-comps/pull-request/663
        https://bugzilla.redhat.com/show_bug.cgi?id=1955884
    
    https://pagure.io/fedora-kickstarts/pull-request/992