Update actions/checkout action to v4 #2401

Job	Run time
Floating Dependencies	1m 54s
Tests	1m 36s
Try: ember-default-with-jquery	3m 10s
Try: ember-default-with-mocha	2m 15s
Try: ember-classic	2m 57s
Try: embroider-safe	2m 53s
Try: embroider-safe-with-mocha	3m 25s
Try: embroider-optimized	2m 53s
Try: embroider-optimized-with-mocha	2m 38s
Try: ember-lts-3.24	2m 29s
Try: ember-lts-3.20	2m 23s
Try: ember-release	2m 27s
Try: ember-beta	3m 30s
Try: ember-canary	2m 48s
Try: ember-qunit-4	2m 32s
	39m 50s

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