Update mixed-reality-add-pins-3d-model.md

Inserted link to coodinate description

Author: iaanw

powerapps-docs/maker/canvas-apps/mixed-reality-add-pins-3d-model.md

@@ -68,10 +68,7 @@ Z dimension (depth) of the pin | PinsZ
 
 
 > [!IMPORTANT]
-> The mixed reality controls use a left-handed coordinate system.
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-<!-- editor note: the following question was here prior to this edit. -->
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+> The mixed reality controls use a [left-handed coordinate system](/windows/uwp/graphics-concepts/coordinate-systems).
 
 
 The following is an example of an Excel table with the required columns: