HDRenderPipeline: Remove unsued variables

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Lighting/LightLoop/LightLoop.cs

     [GenerateHLSL]
     public class LightDefinitions
     {
-        public static int s_MaxNrLightsPerCamera = 1024;
         public static int s_MaxNrBigTileLightsPlusOne = 512;      // may be overkill but the footprint is 2 bits per pixel using uint16.
         public static float s_ViewportScaleZ = 1.0f;