Quaternion docs: Update PG link

[alexchuber]

position vectors are now shared internally since early 7.0, so the PG was broken.

[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[bjsplat]

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[bjsplat]

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[bjsplat]

WebGL2 visualization test reporter:

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