Reverting default X-Requested-With header for xhr

for more details see https://remysharp.com/2011/04/21/getting-cors-working

lib/adapters/xhr.js

@@ -25,9 +25,6 @@ module.exports = function xhrAdapter(resolve, reject, config) {
     config.headers || {}
   );
 
-  // Indicate that request is being made with XHR
-  requestHeaders['X-Requested-With'] = 'XMLHttpRequest';
-
   if (utils.isFormData(data)) {
     delete requestHeaders['Content-Type']; // Let the browser set it
   }

test/specs/headers.spec.js

@@ -9,21 +9,6 @@ describe('headers', function () {
     jasmine.Ajax.uninstall();
   });
 
-  it('should add X-Requested-With header', function (done) {
-    var request;
-
-    axios({
-      url: '/foo'
-    });
-
-    setTimeout(function () {
-      request = jasmine.Ajax.requests.mostRecent();
-
-      expect(request.requestHeaders['X-Requested-With']).toEqual('XMLHttpRequest');
-      done();
-    });
-  });
-
   it('should default common headers', function (done) {
     var request;
     var headers = axios.defaults.headers.common;