Fix arguments type for App.start()

[khrj]

Summary

app.start() doesn't need any arguments if the socket mode receiver (socketMode: true) is used, so the type needs to be changed to support that

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.

Merges khrj/slack-bolt#2

[seratch]

@KhushrajRathod Thanks for taking the time to submit this PR! The CI builds are failing as below. Can you run npx prettier -w src/ && npm test and push the changes?

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! @slack/bolt@3.2.0 lint: `prettier 'src/**/*.ts' --check && eslint --ext .ts src`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the @slack/bolt@3.2.0 lint script.

[khrj]

@seratch Done

[codecov]

Codecov Report

Merging #823 (744bd8b) into main (7d8654c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #823   +/-   ##
=======================================
  Coverage   66.04%   66.04%           
=======================================
  Files          13       13           
  Lines        1172     1172           
  Branches      342      342           
=======================================
  Hits          774      774           
  Misses        333      333           
  Partials       65       65           

Impacted Files	Coverage Δ
src/App.ts	83.63% <ø> (ø)

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[seratch]

Other maintainers will check this early next week (North America time)

[stevengill]

Thanks @KhushrajRathod

[khrj]

Np!