Fix sass deprecations #873

Job	Run time
Tests	54s
Floating Dependencies	1m 11s
ember-lts-4.4	1m 39s
Type checking - typescript-4.2	1m 21s
ember-lts-4.8	1m 33s
Type checking - typescript-4.3	1m 21s
ember-release	1m 30s
Type checking - typescript-4.4	1m 21s
ember-beta	1m 36s
Type checking - typescript-4.5	1m 21s
ember-canary	1m 56s
Type checking - typescript-next	1m 21s
embroider-safe	1m 34s
embroider-optimized	1m 29s
	20m 7s

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