feat: make thread_ts optional for assistant.threads.setSuggestedPrompts

[zimeg]

Summary

This pull request makes the thread_ts argument of assistant.threads.setSuggestedPrompts optional.

Testing

Confirm this no longer raises for a missing thread_ts:

app.client.assistant_threads_setSuggestedPrompts(
    channel_id="C0123456789",
    prompts=[],
)

Category

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

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.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.14%. Comparing base (e23b181) to head (5df6dae).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1901   +/-   ##
=======================================
  Coverage   84.14%   84.14%           
=======================================
  Files         117      117           
  Lines       13356    13362    +6     
=======================================
+ Hits        11238    11244    +6     
  Misses       2118     2118           

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[mwbrooks]

✅ Thank you @zimeg! 🙇🏻

[zimeg]

@mwbrooks I share appreciation to your reviews 💌 So let's get this merged for testing continued!