Fix choose_device import class name in Heroku Helpers

[zackfern]

This is an attempt to fix the ImportError in issue #102:

  File "/app/app.py", line 4, in <module>
    from utils import token_required, call, setup, get_time_args, run_update, as_text, parse_features
  File "/app/utils.py", line 13, in <module>
    from tconnectsync.sync.tandemsource.heroku_helpers import run_oneshot
  File "/app/.heroku/python/lib/python3.9/site-packages/tconnectsync/sync/tandemsource/heroku_helpers.py", line 2, in <module>
    from .choose_device import TandemSourceChooseDevice
ImportError: cannot import name 'TandemSourceChooseDevice' from 'tconnectsync.sync.tandemsource.choose_device' (/app/.heroku/python/lib/python3.9/site-packages/tconnectsync/sync/tandemsource/choose_device.py)

I believe that TandemSourceChooseDevice is not defined in the project and that the file should instead be importing the ChooseDevice class which is defined in sync/tandemsource/choose_device.py

I am not a Python developer, and unfortunately my attempts at testing this change within the context of tconnectsync-heroku have been unsuccessful, so I have not verified this change! I just hope you can validate this fix based off your experience, and hopefully it saves you a little time. 😄 Thank you!

[jwoglom]

Looks right! Thanks for catching the typo