feat(web-api): remove deprecated API methods

[WilliamBergamin]

Summary

Remove long-deprecated Web API methods that have been retired by the Slack platform, along with their associated request/response types and helper utilities.

• files.upload (deprecated in favor of files.uploadV2)
• rtm.start (deprecated in favor of rtm.connect)
• workflows.stepCompleted (Steps from Apps retired September 2024)
• workflows.stepFailed (Steps from Apps retired September 2024)
• workflows.updateStep (Steps from Apps retired September 2024)

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.

[changeset-bot]

⚠️ No Changeset found

Latest commit: fbe4769

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[zimeg]

🌟 Exciting times!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (v8@852a20c). Learn more about missing BASE report.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@          Coverage Diff          @@
##             v8    #2592   +/-   ##
=====================================
  Coverage      ?   87.11%           
=====================================
  Files         ?       62           
  Lines         ?    10186           
  Branches      ?      426           
=====================================
  Hits          ?     8874           
  Misses        ?     1285           
  Partials      ?       27           

Flag	Coverage Δ
cli-hooks	87.11% <100.00%> (?)
cli-test	87.11% <100.00%> (?)
logger	87.11% <100.00%> (?)
oauth	87.11% <100.00%> (?)
socket-mode	87.11% <100.00%> (?)
web-api	87.11% <100.00%> (?)
webhook	87.11% <100.00%> (?)

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