### Describe the bug

After upgrading msw from 1.x to 2.x `FormData` upload stopped working in tests. Looking at the debugging output, Axios doesn't append the `boundary` to the `Content-Type` header anymore.

The MSW team checked [1] this already on their side.

I tried to append the boundary manually to the header for debugging purposes, but that revealed another issue:
```
{ "Content-Type": "multipart/form-data; boundary=abc" }
```
ends in
```
Content-Type: multipart/form-databoundary=abc
```


[1] https://github.com/mswjs/msw/issues/1835


### To Reproduce

Checkout the msw reproducer at [1] and
```
cd examples/with-vitest
npm install
npm test
```


[1] https://github.com/pschyma/msw-examples/tree/axios-formdata-reproducer

### Code snippet

_No response_

### Expected behavior

As with msw the `boundary` is appended to `Content-Type` header.

### Axios Version

1.6.0

### Adapter Version

XHR

### Browser

jsdom

### Browser Version

_No response_

### Node.js Version

18.8.2

### OS

Linux

### Additional Library Versions

```bash
msw 2.0.x
vitest 0.34.6
```


### Additional context/Screenshots

_No response_
lib/platform/browser/index.js
})();
/**
 * Determine if we're running in a standard browser webWorker environment
 *
 * Although the `isStandardBrowserEnv` method indicates that
 * `allows axios to run in a web worker`, the WebWorker will still be
 * filtered out due to its judgment standard
 * `typeof window !== 'undefined' && typeof document !== 'undefined'`.
 * This leads to a problem when axios post `FormData` in webWorker
 */
 const isStandardBrowserWebWorkerEnv = (() => {
  return (
    typeof WorkerGlobalScope !== 'undefined' &&
    
    self instanceof WorkerGlobalScope &&
    typeof self.importScripts === 'function'
  );
})();
export default {
  isBrowser: true,
  classes: {
    URLSearchParams,
    FormData,
    Blob
  },
  isStandardBrowserEnv,
  isStandardBrowserWebWorkerEnv,
  protocols: ['http', 'https', 'file', 'blob', 'url', 'data']
};