Provide guidance that the variable the acceptance application is set on in tests should be nulled out

[notmessenger]

Whatever variable the application instance is assigned to in acceptance tests should also be set to null in an afterEach() to allow garbage collection to function correctly. When done in the mcp codebase the memory footprint decreased around 2.5Gb.

describe('Acceptance Test', function () {
  let application

  beforeEach(function () {
    application = startApp()
  })

  afterEach(function () {
    destroyApp(application)
    application = null
  })