Twenty Seventeen: Remove code and checks for obsolete browsers. #22680

Job	Run time
QUnit Tests / Run QUnit tests	2m 36s
Slack Notifications / Prepare notifications	6s
Slack Notifications / Success notifications	1m 3s
Slack Notifications / Fixed notifications	0s
Slack Notifications / Cancelled notifications	0s
Slack Notifications / Failure notifications	0s
Failed workflow tasks	0s
	3m 45s

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