docs: Fix documented block name for ignored collaborator teams

[tabacco]

Resolves #2550

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Before the change?

• The documentation for the new block from #2481 incorrectly refers to a block named team_ignore in github_repository_collaborators. This block does not exist and will not validate/plan/apply.

After the change?

• Corrects the docs to refer to ignore_team which is the correct block name (per https://github.com/integrations/terraform-provider-github/pull/2481/files#diff-11e4fa718ebd1854d0959e550e09079b0e186f501b720a073719605f1550eb38R79)

Pull request checklist

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

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• [ ] Yes
• [x] No

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[deiga]

Resolves #2721