Remove references to cairisd.py

[failys]

cairisd.py relies on flask_script, which is no longer part of Flask 2. It's not actually required anymore anyway, as appropriately setting FLASK_APP, FLASK_ENV and running flask run --port 7071 does the same thing as 'cairisd.py run server'. Consequently, we should tidy up the documentation to indicate this and remove cairisd.py.