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.)

if (fs.existsSync(refsTmpDir)) {
      console.error("tmp/ exists -- unable to proceed with testing");
      process.exit(1);
    }
    if (fs.existsSync(eqLog)) {
      fs.unlinkSync(eqLog);
    }
    if (fs.existsSync(testResultDir)) {
      testUtils.removeDirSync(testResultDir);
    }
    startTime = Date.now();
    startServer();
    server.hooks.POST.push(refTestPostHandler);
    onAllSessionsClosed = finalize;
    const startUrl = `http:${host}:${server.port}/test/test_slave.html`;
    startBrowsers(function (session) {
      session.masterMode = masterMode;
      session.taskResults = {};
      session.tasks = {};
      session.remaining = manifest.length;
      manifest.forEach(function (item) {
        var rounds = item.rounds || 1;
        var roundsResults = [];
        roundsResults.length = rounds;
        session.taskResults[item.id] = roundsResults;
        session.tasks[item.id] = item;