[#1027] Update websockets package version requirements

[ggml1]

Summary

Closes #1027.

Category (place an x in each of the [ ])

• slack_sdk.web.WebClient (sync/async) (Web API client)
• slack_sdk.webhook.WebhookClient (sync/async) (Incoming Webhook, response_url sender)
• slack_sdk.models (UI component builders)
• slack_sdk.oauth (OAuth Flow Utilities)
• slack_sdk.socket_mode (Socket Mode client)
• slack_sdk.audit_logs (Audit Logs API client)
• slack_sdk.scim (SCIM API client)
• slack_sdk.rtm (RTM client)
• slack_sdk.signature (Request Signature Verifier)
• /docs-src (Documents, have you run ./docs.sh?)
• /docs-src-v2 (Documents, have you run ./docs-v2.sh?)
• /tutorial (PythOnBoardingBot tutorial)
• tests/integration_tests (Automated tests for this library)

Requirements (place an x in each [ ])

• 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 python setup.py validate after making the changes.

[seratch]

Thanks for submitting the pull request! Will merge once the CI builds pass.

[codecov]

Codecov Report

Merging #1028 (b0cad55) into main (1fddbff) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1028      +/-   ##
==========================================
- Coverage   83.70%   83.66%   -0.04%     
==========================================
  Files          95       95              
  Lines        8792     8792              
==========================================
- Hits         7359     7356       -3     
- Misses       1433     1436       +3     

Impacted Files	Coverage Δ
slack_sdk/socket_mode/client.py	69.91% <0.00%> (-2.66%)	⬇️

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