no premature result mutation for Vec2.rotateToRef

[nekochanoide]

for next case:

const vec = new Vector2(offsetX, offsetY);
vec.rotateToRef(angle, vec);

[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]

Snapshot stored with reference name:
refs/pull/13748/merge

Test environment:
https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13748/merge/index.html

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https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13748/merge/index.html#WGZLGJ#4600

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https://sandbox.babylonjs.com/?snapshot=refs/pull/13748/merge
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https://nme.babylonjs.com/?snapshot=refs/pull/13748/merge

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