Removed preview from vector nodes

MaterialGraphProject/Assets/UnityShaderEditor/Runtime/Nodes/Vector1Node.cs

             UpdateNodeAfterDeserialization();
         }
 
-        public override bool hasPreview
-        {
-            get { return true; }
-        }
-
         public sealed override void UpdateNodeAfterDeserialization()
         {
             AddSlot(new MaterialSlot(OutputSlotId, kOutputSlotName, kOutputSlotName, SlotType.Output, SlotValueType.Vector1, Vector4.zero));

MaterialGraphProject/Assets/UnityShaderEditor/Runtime/Nodes/Vector2Node.cs

             UpdateNodeAfterDeserialization();
         }
 
-        public override bool hasPreview
-        {
-            get { return true; }
-        }
-
         public sealed override void UpdateNodeAfterDeserialization()
         {
             AddSlot(new MaterialSlot(kOutputSlotId, kOutputSlotName, kOutputSlotName, SlotType.Output, SlotValueType.Vector2, Vector4.zero));

MaterialGraphProject/Assets/UnityShaderEditor/Runtime/Nodes/Vector3Node.cs

             UpdateNodeAfterDeserialization();
         }
 
-        public override bool hasPreview
-        {
-            get { return true; }
-        }
-
         public sealed override void UpdateNodeAfterDeserialization()
         {
             AddSlot(new MaterialSlot(kOutputSlotId, kOutputSlotName, kOutputSlotName, SlotType.Output, SlotValueType.Vector3, Vector4.zero));

MaterialGraphProject/Assets/UnityShaderEditor/Runtime/Nodes/Vector4Node.cs

             UpdateNodeAfterDeserialization();
         }
 
-        public override bool hasPreview
-        {
-            get { return true; }
-        }
-
         public sealed override void UpdateNodeAfterDeserialization()
         {
             AddSlot(new MaterialSlot(kOutputSlotId, kOutputSlotName, kOutputSlotName, SlotType.Output, SlotValueType.Vector4, Vector4.zero));