### 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/helpers/cookies.js
cookie.push('expires=' + new Date(expires).toGMTString());
        }
        if (utils.isString(path)) {
          cookie.push('path=' + path);
        }
        if (utils.isString(domain)) {
          cookie.push('domain=' + domain);
        }
        if (secure === true) {
          cookie.push('secure');
        }
        document.cookie = cookie.join('; ');
      },
      read: function read(name) {
        const match = document.cookie.match(new RegExp('(^|;\\s*)(' + name + ')=([^;]*)'));
        return (match ? decodeURIComponent(match[3]) : null);
      },
      remove: function remove(name) {
        this.write(name, '', Date.now() - 86400000);
      }
    };
  })() :
  (function nonStandardBrowserEnv() {
    return {
      write: function write() {},
      read: function read() { return null; },
      remove: function remove() {}
    };
  })();