doc: make events in the document clearer

[RhnSharma]

Summary

Fixes #1013
Hi @seratch, I have made the same changes as slackapi/bolt-python#415 to this project.
How does this look? Let me know if this needs any changes.
Thanks

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.

[seratch]

To: assigned reviewers,
The changes look almost the same with the ones fo bolt-python at a glance but, can you check them?

[filmaj]

Looks good! Left one small comment on two missed relevant changes in one of the files. Thanks for tackling this!

[filmaj]

Thanks for the quick turnaround! Looks awesome, appreciate your efforts here 🙏

[codecov]

Codecov Report

Merging #1046 (0a6e652) into main (a2324c6) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1046   +/-   ##
=======================================
  Coverage   68.89%   68.89%           
=======================================
  Files          13       13           
  Lines        1212     1212           
  Branches      357      357           
=======================================
  Hits          835      835           
  Misses        304      304           
  Partials       73       73           

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