Update error message

src/api/Controllers/ObservationConverter.cs

@@ -53,7 +53,7 @@ public override void Write(Utf8JsonWriter writer, Observation value, JsonSeriali
                 JsonSerializer.Serialize(writer, observation, options);
                 break;
             default:
-                throw new NotSupportedException($"Observation type '{value.GetType().Name}' is not supported");
+                throw new NotSupportedException($"Observation type is not supported");
         }
     }
 }