Replacecredentials.valid check for credentials.token_state

[jackwotherspoon]

New best practice for checking validity of credentials is no longer credentials.valid which is now deprecated (as of google-auth v2.24.0). Instead the google-auth folks recommend using credentials.token_state

All instances of the following:

alloydb-python-connector/google/cloud/alloydb/connector/client.py

Lines 164 to 166 in 473f4ab

	if not self._credentials.valid:
	request = Request()
	self._credentials.refresh(request)

Should be replaced to:

from google.auth.credentials import TokenState

# ...
if not self._credentials.token_state == TokenState.FRESH:
    self._credentials.refresh(google.auth.transport.requests.Request())

[jackwotherspoon]

see GoogleCloudPlatform/cloud-sql-python-connector#1089