#### Describe the bug
For some REST API endpoints we use [Google Cloud API Custom Methods](https://cloud.google.com/apis/design/custom_methods) URL design like `/api/resource:customVerb`.

These worked with `axios` prior to **0.27.1** but now they result in an error like:

`AxiosError { message: "Unsupported protocol /api/resource:', code: "ERR_BAD_REQUEST", ... }`

#### To Reproduce
Try to have `axios` get a relative URL with a colon in it, e.g.
```js
axios.get("/api/resource:customVerb");
```

#### Expected behavior
Should continue working as it did before version **0.27.1**.

#### Environment
 - Axios Version: 0.27.1
 - Browser: Microsoft Edge 100.0.1185.50
 - Node.js Version: 16.14.2
 - OS: Windows 10 Pro

#### Additional context/Screenshots
n/a

lib/adapters/xhr.js
if (config.cancelToken) {
        config.cancelToken.unsubscribe(onCanceled);
      }
      if (config.signal) {
        config.signal.removeEventListener('abort', onCanceled);
      }
    }
    if (utils.isFormData(requestData) && utils.isStandardBrowserEnv()) {
      delete requestHeaders['Content-Type']; 
    }
    var request = new XMLHttpRequest();
    
    if (config.auth) {
      var username = config.auth.username || '';
      var password = config.auth.password ? unescape(encodeURIComponent(config.auth.password)) : '';
      requestHeaders.Authorization = 'Basic ' + btoa(username + ':' + password);
    }
    var fullPath = buildFullPath(config.baseURL, config.url);
    request.open(config.method.toUpperCase(), buildURL(fullPath, config.params, config.paramsSerializer), true);
    
    request.timeout = config.timeout;
    function onloadend() {