Review Mozilla 1954988: Deprecate and remove AsyncShutdown.quitApplicationGranted in favor of appShutdownConfirmed

🔍 Bugzilla Audit

Bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=1954988

Commit: 388d4940

In BB 42019: Empty browser's clipboard on browser shutdown, we use AsyncShutdown.quitApplicationGranted, but that has been removed with this Bug.

We should update our patch not to use it, but to use the new thing instead.

At the moment, we have an error at startup.

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