remove Error.captureStackTrace monkey patch as it's no longer necessary with the latest ast-types

lib/6to5/browser.js

@@ -1,21 +1,3 @@
-// this is gross but it monkey patches in behaviour required by `depd` used by
-// `ast-types`
-Error.captureStackTrace = Error.captureStackTrace || function (obj) {
-  if (Error.prepareStackTrace) {
-    var frame = {
-      isEval: function () { return false; },
-      getFileName: function () { return "filename"; },
-      getLineNumber: function () { return 1; },
-      getColumnNumber: function () { return 1; },
-      getFunctionName: function () { return "functionName"; }
-    };
-
-    obj.stack = Error.prepareStackTrace(obj, [frame, frame, frame]);
-  } else {
-    obj.stack = obj.stack || obj.name || "Error";
-  }
-};
-
 var transform = module.exports = require("./transformation/transform");
 
 transform.transform = transform;