Update authorization warning; points to page no longer available.

[ajzobro]

testflinger-cli submit --poll reserve_manta.yaml
Received 401 error from server with reason:

Authentication required for setting timeout: 172800
You are attempting to use a feature that requires client authorisation without using client credentials. 
See https://testflinger.readthedocs.io/en/latest/how-to/authentication.html for more details

Consider pointing to either of:

• https://canonical-testflinger.readthedocs-hosted.com/latest/how-to/authentication/
• https://canonical-testflinger.readthedocs-hosted.com/latest/explanation/authentication/

Note: there is no explaination of how long the "cached" credentials will be cached and the two pages don't link both ways to eachother.

[syncronize-issues-to-jira]

Thank you for reporting your feedback to us!

The internal ticket has been created: https://warthogs.atlassian.net/browse/CERTTF-856.

This message was autogenerated