Fix bug in Vector nodes

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Data/Nodes/Input/Vector/Vector2Node.cs

             if (generationMode.IsPreview())
                 return;
 
-            visitor.AddShaderChunk(precision + " " + GetVariableNameForNode() + " = " + m_Value + ";", true);
+            visitor.AddShaderChunk(precision + "2 " + GetVariableNameForNode() + " = " + precision + "2" + m_Value + ";", true);
         }
 
         public override string GetVariableNameForSlot(int slotId)

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Data/Nodes/Input/Vector/Vector3Node.cs

             if (generationMode.IsPreview())
                 return;
 
-            visitor.AddShaderChunk(precision + " " + GetVariableNameForNode() + " = " + m_Value + ";", true);
+            visitor.AddShaderChunk(precision + "3 " + GetVariableNameForNode() + " = " + precision + "3" + m_Value + ";", true);
         }
 
         public override string GetVariableNameForSlot(int slotId)

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Data/Nodes/Input/Vector/Vector4Node.cs

             if (generationMode.IsPreview())
                 return;
 
-            visitor.AddShaderChunk(precision + " " + GetVariableNameForNode() + " = " + m_Value + ";", true);
+            visitor.AddShaderChunk(precision + "4 " + GetVariableNameForNode() + " = " + precision + "4" + m_Value + ";", true);
         }
 
         public override string GetVariableNameForSlot(int slotId)