Update dependency @ember/test-helpers to v2.8.1

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@ember/test-helpers	2.7.0 -> 2.8.1

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Release Notes

emberjs/ember-test-helpers

v2.8.1

Compare Source

🐛 Bug Fix

• #​1221 Fix issues with embroider-optimized scenarios. (@​rwjblue)

Committers: 1

• Robert Jackson (@​rwjblue)

v2.8.0

Compare Source

🚀 Enhancement

• #​1211 Implement embrerjs/rfcs#​785 (@​cafreeman)
  • Add rerender API
  • Allow render to accept components (e.g. <template></template>).

🐛 Bug Fix

• #​1216 Fix usage of owner.unregister within ember-engines tests (@​buschtoens)

Committers: 2

• Chris Freeman (@​cafreeman)
• Jan Buschtöns (@​buschtoens)

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