fix small typo in comment

ScriptableRenderPipeline/Core/CoreRP/ShaderLibrary/Common.hlsl

 struct PositionInputs
 {
     float3 positionWS;  // World space position (could be camera-relative)
-    float2 positionNDC; // Normalized screen UVs          : [0, 1) (with the float-pixel offset)
+    float2 positionNDC; // Normalized screen UVs          : [0, 1) (with the half-pixel offset)
     uint2  positionSS;  // Screen space pixel coordinates : [0, NumPixels)
     uint2  tileCoord;   // Screen tile coordinates        : [0, NumTiles)
     float  deviceDepth; // Depth from the depth buffer    : [0, 1] (typically reversed)