don't wait for networkidle2 unless a reason to

[peterbe]

Fixes #3116

Prior to this change I would run yarn test:testing headless and sometimes it would break with:

node:internal/process/promises:218
          triggerUncaughtException(err, true /* fromPromise */);
          ^

Error: Navigation failed because browser has disconnected!
    at CDPSession.<anonymous> (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/puppeteer/lib/LifecycleWatcher.js:46:107)
    at CDPSession.emit (node:events:329:20)
    at CDPSession._onClosed (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/puppeteer/lib/Connection.js:215:10)
    at Connection._onMessage (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/puppeteer/lib/Connection.js:105:17)
    at WebSocket.<anonymous> (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/puppeteer/lib/WebSocketTransport.js:44:24)
    at WebSocket.onMessage (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/ws/lib/event-target.js:120:16)
    at WebSocket.emit (node:events:329:20)
    at Receiver.receiverOnMessage (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/ws/lib/websocket.js:789:20)
    at Receiver.emit (node:events:329:20)
    at Receiver.dataMessage (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/ws/lib/receiver.js:422:14)
  -- ASYNC --
    at Frame.<anonymous> (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/puppeteer/lib/helper.js:111:15)
    at Page.waitForNavigation (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/puppeteer/lib/Page.js:692:49)
    at Page.waitForNavigation (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/puppeteer/lib/helper.js:112:23)
    at Object.<anonymous> (/Users/peterbe/dev/MOZILLA/MDN/yari/testing/tests/headless.test.js:35:16)
    at processTicksAndRejections (node:internal/process/task_queues:93:5)
error Command failed with exit code 1.

That error Navigation failed because browser has disconnected! supposedly "means that the node scripts that launched Puppeteer ends without waiting for the Puppeteer actions to be completed.".
So there's something that attempts to close the jest tests without giving the expect-puppeteer a chance to close the browser instance.

I'm more and more unimpressed with expected-puppeteer. It feels like walking on egg shells. And when certain errors happen sometimes, you have no idea where/which line in your *.test.js code that started the headless chrome crashes.

[peterbe]

@schalkneethling @escattone I'm going merge this if/when the CI goes green.