fixing screen coverage LOD for ortho camera

[CraigFeldspar]

No description provided.

[azure-pipelines]

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[azure-pipelines]

Snapshot stored with reference name:
refs/pull/13170/merge

Test environment:
https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13170/merge/index.html

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https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13170/merge/index.html#WGZLGJ#4600

Links to test babylon tools with this snapshot:

https://playground.babylonjs.com/?snapshot=refs/pull/13170/merge
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[Popov72]

See https://forum.babylonjs.com/t/unexpected-behaviour-with-screen-coverage-lods-and-orthographic-camera/35130/3

[sebavan]

Thanks !