custodia: do not use deprecated jwcrypto wrappers
    
    jwcrypto has turned JWK object into a dict-like structure in 2020 and
    marked data wrappers as deprecated. The only exception for direct
    foo['bar'] access is a key ID -- some keys might have no 'kid' property,
    thus it is best to use jwk.get('kid') instead for those.
    
    Fixes: https://pagure.io/freeipa/issue/9597
    
    Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>