VideoCommon: update pixel shader output to match old D3D code

Source/Core/VideoCommon/PixelShaderGen.cpp

@@ -440,7 +440,7 @@ void WritePixelShaderCommonHeader(ShaderCode& out, APIType api_type,
 
   if (bounding_box)
   {
-    out.Write("SSBO_BINDING(0) buffer BBox {{\n"
+    out.Write("SSBO_BINDING(0) coherent buffer BBox {{\n"
               "  int bbox_data[4];\n"
               "}};");