Remove the ``Content-Encoding`` headers from responses
    
    According to RFC7231[0] Content-Encoding is used to indicate the
    response has been encoded using, for example, gzip or base64. It was
    being used to indicate the character encoding used in responses, rather
    than the ``charset=<encoding>`` section of the ``Content-Type`` header.
    This is related to, but does not solve,
    https://pagure.io/pagure/issue/891.
    
    [0] https://tools.ietf.org/html/rfc7231#section-3.1.2
    
    Signed-off-by: Jeremy Cline <jeremy@jcline.org>