Fix nep, should be divided by tland fraction

Author: rbeucher

src/access_moppy/mappings/ACCESS-ESM1.6_mappings.json

@@ -3025,20 +3025,28 @@
             "positive": "down",
             "model_variables": [
                 "fld_s03i262",
-                "fld_s03i293"
+                "fld_s03i293",
+                "fld_s03i395"
             ],
             "calculation": {
                 "type": "formula",
-                "operation": "subtract",
+                "operation": "divide",
                 "args": [
-                    "fld_s03i262",
-                    "fld_s03i293"
+                    {
+                        "operation": "subtract",
+                        "operands": [
+                            "fld_s03i262",
+                            "fld_s03i293"
+                        ]
+                    },
+                    "fld_s03i395"
                 ]
             },
             "CF standard Name": "surface_net_downward_mass_flux_of_carbon_dioxide_expressed_as_carbon_due_to_all_land_processes_excluding_anthropogenic_land_use_change",
             "model_variable_units": {
                 "fld_s03i262": "kg m-2 s-1",
-                "fld_s03i293": "kg m-2 s-1"
+                "fld_s03i293": "kg m-2 s-1",
+                "fld_s03i395": "1"
             }
         },
         "nLand": {