[XR] Remove a 180 degree flip (an old relic)

[RaananW]

Fixes #13447

When initially implemented, right-handed scenes needed a 180 degrees flip because of the way teleportation was working. This code was revamped, but the 180 flip was never removed. I have tested it in different scenarios (and will continue testing it), but it does seem like this is an old relic and technically a bug that needs to be fixed.

[bjsplat]

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[bjsplat]

Snapshot stored with reference name:
refs/pull/13448/merge

Test environment:
https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13448/merge/index.html

To test a playground add it to the URL, for example:

https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13448/merge/index.html#WGZLGJ#4600

Links to test babylon tools with this snapshot:

https://playground.babylonjs.com/?snapshot=refs/pull/13448/merge
https://sandbox.babylonjs.com/?snapshot=refs/pull/13448/merge
https://gui.babylonjs.com/?snapshot=refs/pull/13448/merge
https://nme.babylonjs.com/?snapshot=refs/pull/13448/merge

To test the snapshot in the playground with a playground ID add it after the snapshot query string:

https://playground.babylonjs.com/?snapshot=refs/pull/13448/merge#BCU1XR#0