docs: fixing broken links

[haleychaas]

Summary

Fixing links we've broken over time. These do redirect, but it's cleaner (and eliminates warnings in our docs repo build) to fix them.

Testing

Category

• slack_bolt.App and/or its core components
• slack_bolt.async_app.AsyncApp and/or its core components
• Adapters in slack_bolt.adapter
• Document pages under /docs
• Others

Requirements

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you are agreeing to those rules.

• 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 ./scripts/install_all_and_run_tests.sh after making the changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.34%. Comparing base (76338bf) to head (a8976b4).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@ Coverage Diff @@## main #1532 +/- ##
=======================================
Coverage 91.34% 91.34% =======================================
Files 228 228 Lines 7279 7279 =======================================
Hits 6649 6649 Misses 630 630 

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[mwbrooks]

✅ Looks good!

📝 I edited the PR title to be lowercase to match our convention, since the PR titles become the changelogs.