Bumped Puppeteer to the latest version and switched to the new headless mode

[psmyrek]

Suggested merge commit message (convention)

Internal: Bumped Puppeteer to the latest version and switched to the new headless mode. New Puppeteer includes a fix for handling <iframe> in manual tests that no longer throws connection timeout. Closes ckeditor/ckeditor5#14906.

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Additional information

To do list before merging this PR:

• Wait for new Puppeteer, probably v21.2.0: https://github.com/puppeteer/puppeteer/releases.
• Use new version in this PR.
• Check if issue in Web crawler randomly fails on some manual test on CI ckeditor5#14906 is fixed.

[pomek]

Once we merge the PR, it would be good to revert this change: ckeditor/ckeditor5@a5e3a03.

[coveralls]

coverage: 90.149%. remained the same when pulling 709d960 on fix-crawler-failures-on-ci into 43eabd2 on master.

[psmyrek]

The error with noselection-iframe seems to be fixed, but now not all pages are visited by the crawler. See some logs from CI:

• https://app.circleci.com/pipelines/github/ckeditor/ckeditor5/518/workflows/d3cab551-880e-4762-a16f-be3e7a80a2e8/jobs/2157/parallel-runs/0/steps/0-106
• https://app.circleci.com/pipelines/github/ckeditor/ckeditor5/518/workflows/3c001604-f409-4f04-b7e2-4a3bda6fa85f/jobs/2164/parallel-runs/0/steps/0-106

[psmyrek]

I did a few more checks:

• Installed the newest Puppeteer v21.3.6.
• The new headless: 'new' mode is unstable on CI, but locally it works quite fine. On CI there is always the following error: TargetCloseError: Protocol error (Browser.close): Target closed and Failed to open a new tab - see example job.
• The old headless: 'old' mode works in the same way as previously: the net::ERR_ABORTED is thrown from the noselection-iframe manual test: see example job.

It seems that we should wait for the new stable Chromium release that contains a fix, and then wait for the new Puppeteer that uses the fixed version of the Chromium.