update to v5.4 with ember-cli-update and drop support for Ember < 3.28 #138

Job	Run time
Tests	1m 15s
Floating Dependencies	1m 22s
ember-beta - Allowed to fail	1m 26s
ember-lts-3.28	1m 8s
ember-canary - Allowed to fail	1m 3s
ember-lts-4.4	1m 1s
ember-release-no-deprecations - Allowed to fail	1m 4s
ember-lts-4.8	1m 5s
ember-lts-4.12	1m 2s
ember-release	58s
embroider-safe	1m 5s
embroider-optimized	54s
no-deprecations	47s
	14m 10s

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