Remove image of flow from yaml

[ToshiWakayama-KDDI]

Problem description
Remove the sequence diagram from the yaml file.
The sequence diagram shows the general CAMARA sequence that an access token is retrieved before it is used at an API.
This is not specific to KnowYourCustomer.

Expected action
Remove the sequence diagram from the yaml file.

Additional context
This was originally raised in PR #215 (camaraproject/KnowYourCustomer#215) in the KnowYourCustomer old repository.