chore(deps): update dependency qunit to v2.20.0 (#857) #2260

Job	Run time
Lint Addon	40s
Lint Test App	28s
Tests (ember-4.0, false)	1m 17s
Tests (ember-lts-4.4, false)	1m 12s
embroider-optimized - Allowed to fail	1m 37s
Tests (ember-lts-4.8, false)	1m 25s
ember-beta - Allowed to fail	1m 23s
ember-canary - Allowed to fail	1m 50s
Tests (ember-4.12, false)	1m 10s
Tests (Floating Dependencies)	1m 17s
Tests (ember-default, false)	1m 24s
Tests (ember-release, false)	1m 17s
Tests (embroider-safe, false)	1m 3s
	16m 3s

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