Raise Cinnamon spin max size to 2.6GiB
    
    The maintainer decided on this back in 2019:
    https://pagure.io/fedora-qa/relval/issue/10
    and edited the F31 wiki page:
    https://fedoraproject.org/wiki/Releases/31/Spins
    but the change was dropped in subsequent release wiki pages.
    I don't think there's any process for changing a spin max size
    beyond "maintainer sez so", so this change should probably have
    been kept.
    
    CC @grinnz
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>