fixed particles alpha discard and modulate

ScriptableRenderPipeline/LightweightPipeline/LWRP/ShaderLibrary/Particles.hlsl

 #else
     half result = 1.0h;
 #endif
-    AlphaDiscard(result, cutoff, 0.0001h);
+    AlphaDiscard(alpha, cutoff, 0.0001h);
 
     return result;
 }

ScriptableRenderPipeline/LightweightPipeline/LWRP/ShaderLibrary/ParticlesPBR.hlsl

     surfaceData.smoothness = metallicGloss.g;
     surfaceData.occlusion = 1.0;
 
+    surfaceData.albedo = AlphaModulate(surfaceData.albedo, albedo.a);
-    surfaceData.albedo = AlphaModulate(surfaceData.albedo, surfaceData.alpha);
 }
 
 #endif // LIGHTWEIGHT_PARTICLES_PBR_INCLUDED

ScriptableRenderPipeline/LightweightPipeline/LWRP/Shaders/LightweightStandardParticlesUnlit.shader

                 half4 fragParticleUnlit(VertexOutputLit IN) : SV_Target
                 {
                     half4 albedo = SampleAlbedo(IN, TEXTURE2D_PARAM(_MainTex, sampler_MainTex));
+                    half3 diffuse = AlphaModulate(albedo.rgb, albedo.a);
-                    half3 diffuse = AlphaModulate(albedo.rgb, alpha);
-
+                    
-
                     half fogFactor = IN.posWS.w;
                     ApplyFogColor(result, half3(0, 0, 0), fogFactor);
                     return half4(result, alpha);