fix(branch_protection_v3): ignore context when value exists in checks

[jporzucek]

Resolves #1701

Before the change?

github_branch_protection_v3 flattens all contexts even if they're only configured in checks and if contexts field is empty in required_status_checks.

After the change?

If the context is already in checks, it's not parsed into context field.

Pull request checklist

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

• Yes
• No

It doesn't break anything since contexts in checks are still applied and they'll be applied by GitHub to contexts.

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[bahag-hammera]

@jporzucek Is there an Update on this PR we are waiting heavily on this fix :) @kfcampbell

[jporzucek]

@kfcampbell Can you take a look at this PR when you have a chance pls? 🙏

[rsi-mrobinson]

would be super duper awesome if someone could put eyes on this PR that potentially fixes a super annoying bug. Pretty disappointing that this has been sitting open since april.

[stevehipwell]

@jporzucek I've been able to fix this issue in the acceptance tests by setting Computed: true for both contexts & checks which AFAIK is the idiomatic solution. So I don't think you need this additional code.