docs: remove invalid copilot_code_review fields

[XiaoPengMei]

Closes #3308

Summary

• remove allowed_merge_methods and required_reviewers from the rules.copilot_code_review docs in both repository and organization ruleset pages
• keep the documentation aligned with the provider schema, where copilot_code_review only supports review_on_push and review_draft_pull_requests

[github-actions]

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