chore(deps): update dependency @ember/test-helpers to ^2.9.4 #1287

Job	Run time
Floating Dependencies (16)	47s
Check Types	47s
Base Tests (16)	1m 13s
Floating Dependencies (18)	55s
Base Tests (18)	1m 15s
Compatibility (ember-4.4)	1m 50s
Compatibility (ember-4.8)	1m 48s
Compatibility (ember-release)	1m 50s
Compatibility (ember-beta)	1m 55s
Compatibility (ember-canary)	1m 54s
Compatibility (embroider)	1m 38s
Release	0s
ember-cli-update	0s
	15m 52s

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