Remove a magic number

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitData.hlsl

     // Ambient occlusion is cosine weighted, thus use following equation. See slide 129
     float cosAv = sqrt(1.0 - surfaceData.ambientOcclusion);
     float roughness = max(PerceptualSmoothnessToRoughness(surfaceData.perceptualSmoothness), 0.01); // Clamp to 0.01 to avoid edge cases
-    float cosAs = exp2(-3.32193 * Sq(roughness));
+    float cosAs = exp2((-log(10.0)/log(2.0)) * Sq(roughness));
     float cosB = dot(bentNormalWS, reflect(-V, surfaceData.normalWS));
 
     return SphericalCapIntersectionSolidArea(cosAv, cosAs, cosB) / (TWO_PI * (1.0 - cosAs));