#### Is your feature request related to a problem? Please describe.
This is an optimazition of code.

#### Describe the solution you'd like
The following line of code comes from https://github.com/axios/axios/blob/master/lib/adapters/http.js#L403:
```js
reject(!cancel || (cancel && cancel.type) ? new CanceledError() : cancel);
```
It can be optimized as follows:
```js
reject(!cancel || cancel.type ? new CanceledError() : cancel);
```

#### Describe alternatives you've considered
When the code is executed to `(cancel && cancel.type)`, it means `!cancel` is false, so `cancel` is true, we can get `cancel.type` directly.

#### Additional context
no more

lib/adapters/http.js
if (!headers[headerNames['user-agent']]) {
        delete headers[headerNames['user-agent']];
      }
      
    } else {
      
      headers['User-Agent'] = 'axios/' + VERSION;
    }
    
    if (utils.isFormData(data) && utils.isFunction(data.getHeaders)) {
      Object.assign(headers, data.getHeaders());
    } else if (data && !utils.isStream(data)) {
      if (Buffer.isBuffer(data)) {
        
      } else if (utils.isArrayBuffer(data)) {
        data = Buffer.from(new Uint8Array(data));
      } else if (utils.isString(data)) {
        data = Buffer.from(data, 'utf-8');
      } else {
        return reject(new AxiosError(
          'Data after transformation must be a string, an ArrayBuffer, a Buffer, or a Stream',
          AxiosError.ERR_BAD_REQUEST,
          config
        ));
      }
      if (config.maxBodyLength > -1 && data.length > config.maxBodyLength) {
        return reject(new AxiosError(
          'Request body larger than maxBodyLength limit',
          AxiosError.ERR_BAD_REQUEST,