Update dependency ember-cli to v6 #1459

Job	Run time
Tests	1m 2s
Floating Dependencies	48s
no-deprecations	45s
ember-lts-5.12	44s
ember-lts-4.4	46s
ember-lts-4.8	55s
ember-release	46s
ember-lts-4.12	1m 27s
ember-lts-3.28	48s
ember-canary	46s
ember-beta	45s
embroider-safe	52s
ember-release-no-deprecations	1m 4s
ember-modifier-3.2.7	44s
embroider-optimized	1m 23s
	13m 35s

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