Update dependency pytest to v6

This MR contains the following updates:

Package	Type	Update	Change
pytest	dev-dependencies	major	^5.4.2 -> ^6.0.0

---

Renovate configuration

📅 Schedule: At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this MR and you won't be reminded about this update again.

---

• If you want to rebase/retry this MR, check this box

---

This MR has been generated by Renovate Bot.