update to v4.8 with ember-cli-update #331

Job	Run time
Floating Dependencies	1m 55s
Tests	1m 53s
Percy Tests	3m 23s
ember-lts-3.16	1m 34s
ember-canary - Allowed to fail	2m 42s
ember-lts-3.20	1m 4s
ember-release-no-deprecations - Allowed to fail	2m 44s
ember-lts-3.24	1m 36s
ember-lts-3.28	3m 43s
ember-lts-4.4	2m 25s
ember-release	2m 56s
ember-beta	3m 12s
ember-classic	3m 11s
ember-default-with-jquery	53s
embroider-safe	3m 38s
embroider-optimized	2m 54s
no-deprecations	3m 3s
	42m 46s

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