chore: address TODO for app.makeSingleInstance / releaseSingleInstance removal

[miniak]

Description of Change

// TODO(MarshallOfSound): Remove in 4.0
app.releaseSingleInstance = () => {
  deprecate.warn('app.releaseSingleInstance(cb)', 'app.releaseSingleInstanceLock()')
  app.releaseSingleInstanceLock()
}

// TODO(MarshallOfSound): Remove in 4.0
app.makeSingleInstance = (oldStyleFn) => {
  deprecate.warn('app.makeSingleInstance(cb)', 'app.requestSingleInstanceLock() and app.on(\'second-instance\', cb)')
  if (oldStyleFn && typeof oldStyleFn === 'function') {
    app.on('second-instance', (event, ...args) => oldStyleFn(...args))
  }
  return !app.requestSingleInstanceLock()
}

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• PR title follows semantic commit guidelines

Release Notes

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[release-clerk]

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