Remove warning in gradient sky shader

com.unity.render-pipelines.high-definition/HDRP/Editor/Sky/HDRISky/HDRISkyEditor.cs

             if (hdri == null)
                 return;
 
-            float omegaP = (Mathf.PI * 4) / (6.0f * hdri.width * hdri.width);
             m_IntegrateHDRISkyMaterial.SetTexture(HDShaderIDs._Cubemap, hdri);
 
             Graphics.Blit(Texture2D.whiteTexture, m_IntensityTexture.rt, m_IntegrateHDRISkyMaterial);

com.unity.render-pipelines.high-definition/HDRP/Sky/GradientSky/GradientSky.shader

         float verticalGradient = viewDirWS.y * _GradientDiffusion;
 		float topLerpFactor = saturate(-verticalGradient);
 		float bottomLerpFactor = saturate(verticalGradient);
-		float3 color = lerp(_GradientMiddle,_GradientBottom,bottomLerpFactor);
-		color = lerp(color.xyz,_GradientTop,topLerpFactor);
-		return float4 (color.xyz,1);
+		float3 color = lerp(_GradientMiddle.xyz, _GradientBottom.xyz, bottomLerpFactor);
+		color = lerp(color, _GradientTop.xyz, topLerpFactor);
+		return float4 (color, 1.0);
     }