Finalize session does not get called

[drikusroor]

Describe the bug
The so called finalizeSession endpoint does not get called at the end of a session in the frontend (anymore). Calling this endpoint tells the backend that the session is over. It used to be called, but somewhere during development the call got removed. See also this PR comment

To Reproduce
Steps to reproduce the behavior:

1. Start any experiment
2. Keep the developers tools open in your browser on the network tab
3. Finish it
4. Check the network tab and confirm that /session/{id}/finalize does not get called

Expected behavior
The finalize session endpoint does get called when the session is over

Screenshots
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Desktop (please complete the following information):
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Smartphone (please complete the following information):
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Additional context
Related to #598 and #660