docs: typo for conversations in chat stream docs

[zimeg]

Summary

This PR fixes a typo for the word "conversations" found from the kind @lukegalbraithrussell in slackapi/node-slack-sdk#2392!

Testing

📚 Code has been generated and documentation updated!

Category

• slack_sdk.web.WebClient (sync/async) (Web API client)
• /docs (Documents)

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.

[lukegalbraithrussell]

🎤

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (ai-apps@8330c20). Learn more about missing BASE report.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@ Coverage Diff @@## ai-apps #1762 +/- ##
==========================================
Coverage ? 85.12% ==========================================
Files ? 115 Lines ? 13068 Branches ? 0 ==========================================
Hits ? 11124 Misses ? 1944 Partials ? 0 

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[zimeg]

@lukegalbraithrussell Thanks for kind review and findings 🎶