Remove nextcloud taiko tests from Stackspin repo
We currently have nextcloud taiko tests in two places:
- in the nextcloud repo, run by helm test as part of that repo's CI;
- in the stackspin repo, as we have it for other apps.
Basically 2. is still lingering even though we moved the tests to 1. To prevent all kinds of confusion and double work, we should really remove the nextcloud taiko tests from stackspin, and run them in the stackspin CI via helm test
instead.