Fixed the issues that was causing the direcitonal lightmaps to be overbright.

ScriptableRenderPipeline/LightweightPipeline/Shaders/LightweightCore.cginc

 
 #if DIRLIGHTMAP_COMBINED
     half4 bakedDirection = UNITY_SAMPLE_TEX2D_SAMPLER(unity_LightmapInd, unity_Lightmap, lightmapUV);
-    bakedColor += DecodeDirectionalLightmap(bakedColor, bakedDirection, normalWS);
+    bakedColor = DecodeDirectionalLightmap(bakedColor, bakedDirection, normalWS);
 #endif
 
     return bakedColor;