Update RTM docs

[ryan-aldaz]

Summary

Fix #1145

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.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-src (Documents, have you run ./scripts/docs.sh?)
• /docs-src-v2 (Documents, have you run ./scripts/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 python3 -m venv .venv && source .venv/bin/activate && ./scripts/run_validation.sh after making the changes.

[CLAassistant]

All committers have signed the CLA.

[srajiang]

@ryan-aldaz - Woot, thanks for the contribution Ryan! Mind signing the CLA?

[codecov]

Codecov Report

Merging #1290 (e258db2) into main (2f926a6) will decrease coverage by 0.01%.
The diff coverage is n/a.

❗ Current head e258db2 differs from pull request most recent head 180a0e1. Consider uploading reports for the commit 180a0e1 to get more accurate results

@@            Coverage Diff             @@
##             main    #1290      +/-   ##
==========================================
- Coverage   85.63%   85.62%   -0.02%     
==========================================
  Files          84       84              
  Lines        7827     7827              
==========================================
- Hits         6703     6702       -1     
- Misses       1124     1125       +1     

Impacted Files	Coverage Δ
slack_sdk/socket_mode/builtin/internals.py	72.10% <0.00%> (-0.43%)	⬇️

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[srajiang]

Suggested change

	**rtm.start method deprecation after Nov 30th, 2021.** see details `here <https://api.slack.com/changelog/2021-10-rtm-start-to-stop>`_
	**rtm.start method has been deprecated for apps created after Nov 30th, 2021.** see details `here <https://api.slack.com/changelog/2021-10-rtm-start-to-stop>`_

[ryan-aldaz]

isn't it fully deprecated?

[srajiang]

The announcement has this caveat:

For apps created before November 30, 2021, making API calls to https://slack.com/api/rtm.start will still technically succeed and return successful, but highly truncated responses even after September 27, 2022.

Seems like newly created apps after the date must use rtm.connect, and older apps will receive responses from rtm.start that are identical to rtm.connect. Is that your reading as well?

[ryan-aldaz]

Ahh i see Thank you!
I signed the CLA

[seratch]

Thank you very much for improving this document!