RS Connector requiring a valid aws identity to connect to Redshift, when that shouldn't be required

## Driver version
2.0.0

## Redshift version
PostgreSQL 8.0.2 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.4.2 20041017 (Red Hat 3.4.2-6.fc3), Redshift 1.0.76832

## Client Operating System
macos ventura 13.6 (22G120)

## Python version
Python 3.12.4

## Table schema
n/a

## Problem description
redshift_connector is trying to grab a valid aws identity when just doing a simple connect to Redshift. This is causing issues for us as we have users that do not have a valid aws identity, that need to connect to Redshift. Importantly, they are able to connect to Redshift using various SQL clients, the same behavior should be expected with Redshift connector.

## Python Driver trace logs
would prefer to not post this

## Reproduction code
def get_redshift_connection_robotic():
try:
conn = redshift_connector.connect(
iam=True,
ssl=True,
host='',
port=5439,
database='',
cluster_identifier='',
region='us-east-1',
partner_sp_id='',
idp_host='',
credentials_provider='PingCredentialsProvider',
user='',
password=''
)
conn.autocommit = True
cursor = conn.cursor()
cursor.execute('SELECT 1;')
print(cursor.fetchall())
except Exception as error:
logging.error("Error connecting to Redshift:", exc_info=True)

if __name__ == "__main__":
get_redshift_connection_robotic()

Start with the get_redshift_connection_robotic reproduction and trace the IAM and PingCredentialsProvider connection path. Compare the connector's identity requirement with the reported SQL-client behavior; done means a user without a valid AWS identity can connect to Redshift with the shown configuration and SELECT 1 succeeds.

索引モデルが issue の本文から書いたものです。