Uncap max version of importlib-metadata
    
    Upstream, it sets < 6.3, however we ship 6.8 in RDO and I don't see any
    valid justification for capping max version, so let us just use what is
    in RDO repo.
    
    Related-to: https://review.rdoproject.org/r/q/Ic46f9c24e883ce672f0bcbf8ba2edd723d80923b