WIP [Python3.9] prevent interpreter shutdown error

[GuillaumeDSM]

Fixes the interpreter shutdown error however prevents the bot from stopping, hence the WIP

It looks like the issue is that threadpoolexecutors are not daemons anymore and need to be shutdown (https://docs.python.org/3/library/concurrent.futures.html#concurrent.futures.Executor.shutdown)

[github-actions[bot]]

Your preview environment pr-1852-octobot-drakkarsoftware has been deployed with errors.

[Herklos]

Now in the code base.