Update 'Granting Dodona Access' sections to reflect automated GitHub invitation acceptance

[TomNaessens]

Related to https://github.com/dodona-edu/dodona/issues/6144, updates the docs now that we have automated collaboration invite acceptance again.

We schedule the jobs every 10 minutes, but this is just an indication to GitHub. Looking at the latest runs, it can take up to +- 25 minutes in between runs, so mentioning 30 gives the user an indication while also not overpromising the time it can take.

Open for any rewordings, this is the best GPT 4.1 could come up with that I found acceptable 😄

[Copilot]

Pull Request Overview

Updates documentation to reflect automated GitHub invitation acceptance, replacing previous manual process information. This change aligns the documentation with the new automated system implemented for handling collaboration invites.

• Replaces references to manual invitation acceptance with automated process
• Updates timing expectations from indefinite wait to up to 30 minutes
• Modifies warning box titles and content to reflect the new process

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
nl/guides/exercises/creating-exercises/setup/index.md	Updates Dutch documentation warning from manual to automated process
en/guides/exercises/creating-exercises/setup/index.md	Updates English documentation warning from manual to automated process

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[bmesuere]

This should probably also be added on https://docs.dodona.be/en/guides/exercises/new-exercise-repo/ and https://docs.dodona.be/nl/guides/exercises/new-exercise-repo/

[TomNaessens]

This should probably also be added on https://docs.dodona.be/en/guides/exercises/new-exercise-repo/ and https://docs.dodona.be/nl/guides/exercises/new-exercise-repo/

What happens at this moment for UGent Github/Github enterprise/Gitlab invites? Do we manually accept those?

[chvp]

Both for UGent GitHub and Gitlab we do not need to accept but are added automatically. I would assume that for other GitHub Enterprise instances this would be the same.