fix(slack): request reactions:read in OAuth URL, drop im:history #4856

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Final Result: Bugbot completed review - no issues found! ✅

Request ID: serverGenReqId_5a3c22fb-ed91-46a2-892e-c7b3bcea7c31

✅ Bugbot reviewed your changes and found no new issues!

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^{Reviewed by Cursor Bugbot for commit 0543dcc. Configure here.}