Don't ship playwright tests in production

[jvoisin]

Describe the bug

The viewer app on my nextcloud instance weights 74.2 MiB, amongst which 57.9 MiB are from the playwright/ folder. That's around ~80% of useless weight, as playwright is for testing/CI, and is completely unused in production. It would be nice to not ship this folder to every nextcloud instance.

To Reproduce
Steps to reproduce the behavior:

1. Deploy Nextcloud with the viewer app
2. Look at the filesystem
3. See a 57.9 MiB folder named playwright there