Drop the custom /etc/containers/toolbox.conf from RHEL 10 onwards
    
    Complete support for RHEL Toolbx images based on the Red Hat Universal
    Base Images (or UBI) was only recently added to Toolbx [1], in version
    0.0.99.4.  Before that, Toolbx would only pick the image for RHEL 8,
    and even before that, it would pick the base 'ubi8' image, which isn't
    designed for interactive command line use.
    
    Due to this, RHEL >= 8.5 shipped a custom configuration file
    in /etc/containers/toolbox.conf to specify the image.
    
    However, that's not necessary anymore.  RHEL 10 is going to be a fresh
    new operating system, and it will be better if we don't ship any custom
    configuration that's not needed, because it will ensure consistency with
    non-RHEL operating systems, including Fedora.
    
    [1] Upstream commit 0a29b374e649437
        https://github.com/containers/toolbox/commit/0a29b374e649437
        https://github.com/containers/toolbox/issues/1065