docs: removing external links for unified nav

[haleychaas]

Summary

I'm working on uniting the nav bar for all of the tools so that you don't lose the context of the rest of the nav when you click on one of the tools. In this PR, I'm removing the external links (release notes, github repo, contributor's guide) to cut down on bloat in the nav menu when they are all united. Since the github repo and contributor's guide are already mentioned in the landing page, I just added the release notes link to that.

Preview for one nav here: https://docs-slack-d-unified-na-idfrpr.herokuapp.com/tools
PR for unified nav here: https://github.com/slackapi/docs/pull/605

Testing

Category

• slack_sdk.web.WebClient (sync/async) (Web API client)
• slack_sdk.webhook.WebhookClient (sync/async) (Incoming Webhook, response_url sender)
• slack_sdk.socket_mode (Socket Mode client)
• slack_sdk.signature (Request Signature Verifier)
• slack_sdk.oauth (OAuth Flow Utilities)
• slack_sdk.models (UI component builders)
• slack_sdk.scim (SCIM API client)
• slack_sdk.audit_logs (Audit Logs API client)
• slack_sdk.rtm_v2 (RTM client)
• /docs (Documents)
• /tutorial (PythOnBoardingBot tutorial)
• tests/integration_tests (Automated tests for this library)

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run python3 -m venv .venv && source .venv/bin/activate && ./scripts/run_validation.sh after making the changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.14%. Comparing base (0b4f57b) to head (aa31a53).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@ Coverage Diff @@## main #1895 +/- ##
=======================================
Coverage 84.14% 84.14% =======================================
Files 117 117 Lines 13356 13356 =======================================
Hits 11238 11238 Misses 2118 2118 

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[zimeg]

@haleychaas LGTM! Same ordering suggestion as the Bolt for Python PR - is moving "Release notes" before "Contributing" alright for a first read?

• Getting help
• Release notes
• Contributing

Feel free to merge whenever best! 📰