As can be seen from the first round of testing in PR #15864, trying to update Puppeteer beyond version `19.0.0` completely breaks testing in Firefox. Curiously it does work locally when the `--noChrome` flag is being used, so it seems to be an issue with running tests in both Chrome *and* Firefox in parallel.

We need to fix this, likely by making some adjustments to our test-suite, such that we don't get "stuck" on an older version of Puppeteer without being able to update. (A temporary work-around could also be to disable testing in Chrome.)

"pdfjs.disabled": true,
      "browser.helperApps.neverAsk.saveToDisk": "application/pdf",
      
      "browser.download.always_ask_before_handling_new_types": true,
      "browser.download.panel.shown": true,
      "browser.download.alwaysOpenPanel": false,
      
      "browser.download.folderList": 2,
      "browser.download.dir": tempDir,
      
      "print.always_print_silent": true,
      "print.show_print_progress": false,
      print_printer: "PDF",
      "print.printer_PDF.print_to_file": true,
      "print.printer_PDF.print_to_filename": printFile,
      
      "gfx.offscreencanvas.enabled": true,
      
      "gfx.canvas.accelerated": false,
    };
  }
  const browser = await puppeteer.launch(options);
  if (startUrl) {
    const pages = await browser.pages();
    const page = pages[0];
    await page.goto(startUrl, { timeout: 0, waitUntil: "domcontentloaded" });
  }
  return browser;
}
function startBrowsers(initSessionCallback, makeStartUrl = null) {