Remove unused fields from export_csv

rev 2fe23af89625 removed from the caller.

issue11886
review441721003

src/window.js

@@ -2021,7 +2021,7 @@
                 this.destroy();
             }
         },
-        export_csv: function(fields, data, paths) {
+        export_csv: function(data, paths) {
             var locale_format = this.el_csv_locale.prop('checked');
             var unparse_obj = {};
             unparse_obj.data = data.map(function(row, i) {