Update content to remove redundant Robust math types (#38930)

Vector3, Vector4, Matrix4, and Quaternion are now gone. This switches us over to System.Numerics where applicable.

Content.Client/Holopad/HolopadSystem.cs

@@ -5,6 +5,7 @@ using Robust.Client.Graphics;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Timing;
 using System.Linq;
+using System.Numerics;
 using DrawDepth = Content.Shared.DrawDepth.DrawDepth;
 
 namespace Content.Client.Holopad;