* and stop setting default values in python operator code, so defaults can be set at the server side.

This issue is just for the PR and questions from maintainers. 
setup.py
'slack_sdk>=3.0.0,<4.0.0',
]
snowflake = [
    'snowflake-connector-python>=2.4.1',
    'snowflake-sqlalchemy>=1.1.0',
]
spark = [
    'pyspark',
]
ssh = [
    'paramiko>=2.6.0',
    'pysftp>=0.2.9',
    'sshtunnel>=0.1.4,<0.2',
]
statsd = [
    'statsd>=3.3.0, <4.0',
]
tableau = [
    'tableauserverclient',
]
telegram = [
    'python-telegram-bot~=13.0',
]
trino = ['trino']
vertica = [
    'vertica-python>=0.5.1',
]
virtualenv = [
    'virtualenv',
]