fix(SnapDropZone): remove shadows from highlight object

The highlight object on the Snap Drop Zone was casting a shadow and
was also set to receive shadows. This fix forces all mesh renderers
of the snap drop zone to not cast or receive shadows.

Author: thestonefox

Assets/VRTK/Prefabs/Internal/Scripts/VRTK_SnapDropZone.cs

@@ -350,6 +350,7 @@ protected virtual void OnEnable()
             }
 #pragma warning restore 618
 
+            DisableHighlightShadows();
             if (!VRTK_SharedMethods.IsEditTime() && Application.isPlaying && defaultSnappedInteractableObject != null)
             {
                 ForceSnap(defaultSnappedInteractableObject);
@@ -586,6 +587,19 @@ protected virtual void GenerateContainer()
             }
         }
 
+        protected virtual void DisableHighlightShadows()
+        {
+            if (highlightObject != null)
+            {
+                Renderer[] foundRenderers = highlightObject.GetComponentsInChildren<Renderer>(true);
+                for (int i = 0; i < foundRenderers.Length; i++)
+                {
+                    foundRenderers[i].receiveShadows = false;
+                    foundRenderers[i].shadowCastingMode = UnityEngine.Rendering.ShadowCastingMode.Off;
+                }
+            }
+        }
+
         protected virtual void SetContainer()
         {
             Transform findContainer = transform.Find(HIGHLIGHT_CONTAINER_NAME);
@@ -936,6 +950,7 @@ protected virtual void GenerateHighlightObject()
                 DeleteHighlightObject();
             }
 
+            DisableHighlightShadows();
             SetHighlightObjectActive(false);
             SetContainer();
         }