[FIX] Restore collision gizmo render style

[willeastcott]

Fixes #1651

Avoid overwriting the 'behind' alpha value.

Also, strip some redundant property sets (MeshInstance#castShadow defaults to false and MeshInstance#drawToDepth doesn't exist).

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[Copilot]

Pull request overview

This PR fixes collision gizmo render styling by preventing the "behind" material's alpha value from being incorrectly overwritten and removes redundant property settings.

• Removes the incorrect uColor parameter set on the behind mesh instance material that was overwriting the correct alpha value
• Removes redundant drawToDepth = false settings since this is already handled by the material's depthWrite property
• Removes various redundant castShadow = false property settings

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

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