update mapping for detoc (#473)

Author: rhaegar325

src/access_moppy/mappings/ACCESS-ESM1-5_mappings.json

@@ -5920,19 +5920,13 @@
                 "type": "formula",
                 "operation": "multiply",
                 "args": [
-                    {
-                        "operation": "multiply",
-                        "args": [
-                            "det",
-                            1000
-                        ]
-                    },
-                    1.035
+                    "det",
+                    0.001
                 ]
             },
             "CF standard Name": "mass_concentration_of_detrital_organic_matter_expressed_as_carbon_in_sea_water",
             "model_variable_units": {
-                "det": "mol kg-1"
+                "det": "mmol m-3"
             }
         },
         "dfe": {