remove default value

mixins/getDeviceType.js

@@ -25,7 +25,7 @@ export default {
      */
     getSign() {
       const sign = {
-        x_app: 'ios 4.6.0',
+        // x_app: 'ios 4.6.0',
         x_nonce_str: '1558105441627',
         x_signature: 'h5'
       };