HDRenderPipeline: Remove multiplicative mode 2

ScriptableRenderPipeline/HDRenderPipeline/Material/Unlit/Editor/BaseUnlitUI.cs

                             material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.One);
                             break;
 
-                        // Multiplicative
-                        // color: src * dst
-                        case BlendMode.Multiplicative:
-                            material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.DstColor);
-                            material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.Zero);
-                            break;
-
                         // PremultipliedAlpha
                         // color: src * src_a + dst * (1 - src_a)
                         // src is supposed to have been multiplied by alpha in the texture on artists side.