Removes the association of a particular client to a keyword.

def RemoveClientKeyword(self, client_id, keyword, cursor=None):
    """Removes the association of a particular client to a keyword."""
    cursor.execute(
        "DELETE FROM client_keywords "
        "WHERE client_id = %s AND keyword_hash = %s",
        [db_utils.ClientIDToInt(client_id),
         mysql_utils.Hash(keyword)])