chore: firefox crashes upstream + keyboard shortcuts changed

[aslushnikov]

The new roll fails 2 tests on mac:

• capabilities.spec.ts - should play video crashes. This is due to upstream regression that is filed as P1. With this regression, current tip-of-tree firefox headless (Mozilla Firefox 88.0a1) is crashing when trying to play videos, e.g. loading our video test asset:

  $ # the following crashes
  $ /Applications/Firefox\ Nightly.app/Contents/MacOS/firefox --headless file:///Users/aslushnikov/prog/playwright/test/assets/video.html
  $ # hotfix - MOZ_WEBRENDER=0
  $ MOZ_WEBRENDER=0 /Applications/Firefox\ Nightly.app/Contents/MacOS/firefox --headless file:///Users/aslushnikov/prog/playwright/test/assets/video.html

• page-keyboard.spec.ts - should support MacOS shortcuts - fails. This is due to upstream changes to the native shortcut resolving - https://phabricator.services.mozilla.com/D102877 The new logic hardcodes the "default layout" for Mac, and it looks like the obscure shortcut we use in tests is not part of this hardcoded list. We discussed this with Joel and decided to disable the test for now and let him decide later what to do with it.

[aslushnikov]

For the record: we tried rolling onto it and failed on mac: https://github.com/microsoft/playwright/runs/2021159243

[aslushnikov]

Upstream crash bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1697004