update to v5.4 with ember-cli-update and drop support for Ember < 3.28 #137

Job	Run time
Tests	1m 23s
Floating Dependencies	1m 17s
ember-beta - Allowed to fail	55s
ember-lts-3.28	28s
ember-canary - Allowed to fail	1m 1s
ember-lts-4.4	50s
ember-release-no-deprecations - Allowed to fail	1m 12s
ember-lts-4.8	52s
ember-lts-4.12	47s
ember-release	1m 0s
embroider-safe	1m 15s
embroider-optimized	48s
no-deprecations	54s
	12m 42s

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