update to v4.8 with ember-cli-update #327

Job	Run time
Percy Tests	2m 38s
Floating Dependencies	1m 48s
Tests	1m 32s
ember-canary - Allowed to fail	3m 56s
ember-release-no-deprecations - Allowed to fail	3m 30s
ember-lts-3.16	2m 34s
ember-lts-3.20	3m 50s
ember-lts-3.24	2m 51s
ember-lts-3.28	4m 19s
ember-release	4m 5s
ember-beta	3m 44s
ember-classic	3m 13s
ember-default-with-jquery	51s
embroider-safe	3m 41s
embroider-optimized	3m 19s
no-deprecations	3m 57s
	49m 48s

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