Rig origin changes break absolute-world-placed unit tests

[Zee2]

This issue has been migrated a new MRTK repository, and the status of this issue will now be tracked at the following location:

• Rig origin changes break absolute-world-placed unit tests MixedRealityToolkit/MixedRealityToolkit-Unity#346

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Describe the bug

When #11035 changed the XR Rig to specify user height and origin offset explicitly, unit tests that expected y=0 for head height broke.

To reproduce

Run unit tests. Unit tests fail.

Expected behavior

Unit tests should not fail.

Fix

Objects in unit tests should be placed in head-height-relative reference frame.