#### 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
auth = urlUsername + ':' + urlPassword;
    }
    if (auth && headerNames.authorization) {
      delete headers[headerNames.authorization];
    }
    var isHttpsRequest = isHttps.test(protocol);
    var agent = isHttpsRequest ? config.httpsAgent : config.httpAgent;
    try {
      buildURL(parsed.path, config.params, config.paramsSerializer).replace(/^\?/, '');
    } catch (err) {
      var customErr = new Error(err.message);
      customErr.config = config;
      customErr.url = config.url;
      customErr.exists = true;
      reject(customErr);
    }
    var options = {
      path: buildURL(parsed.path, config.params, config.paramsSerializer).replace(/^\?/, ''),
      method: config.method.toUpperCase(),
      headers: headers,
      agent: agent,
      agents: { http: config.httpAgent, https: config.httpsAgent },
      auth: auth
    };
    if (config.socketPath) {
      options.socketPath = config.socketPath;
    } else {
      options.hostname = parsed.hostname;
      options.port = parsed.port;
    }