### Describe the bug

`AxiosHeaders` types makes it so trying to call methods on the instance raises a `typescript` compilation error.

<img width="1142" alt="image" src="https://user-images.githubusercontent.com/476069/209943677-fa7775e7-0f23-4b86-88ae-ad28df8c0533.png">

`AxiosRequestConfig.headers` can be either `RawAxiosRequestHeaders` or `AxiosHeaders`. `RawAxiosRequestHeaders`, being an alias of `Record<string, AxiosHeaderValue>` causes methods to not be callable.

### To Reproduce

Invoke any method on `AxiosRequestConfig.headers`.

### Code snippet

```js
const api = axios.create({ ... })

api.interceptors.request.use(req => {
  // Trying to access any method on `req.headers` will result in
  // a "This expression is not callable" TS error
  req.headers.set('foo', 'bar')
})
```


### Expected behavior

Should be able to call any method declared in `AxiosHeaders`.

### Environment

* `axios`: `1.2.2`
* `node`: `18.12.1`
* `typescript`: `4.9.4`
* macOS Ventura `13.1` 

test/module/typings/cjs/index.ts
axios.delete<User, string>('/user')
    .then(handleStringResponse)
    .catch(handleError);
axios.post<Partial<UserCreationDef>, string>('/user', { name: 'foo' })
    .then(handleStringResponse)
    .catch(handleError);
axios.post<Partial<UserCreationDef>, string>('/user', { name: 'foo' }, { headers: { 'X-FOO': 'bar' } })
    .then(handleStringResponse)
    .catch(handleError);
axios.put<Partial<UserCreationDef>, string>('/user', { name: 'foo' })
    .then(handleStringResponse)
    .catch(handleError);
axios.patch<Partial<UserCreationDef>, string>('/user', { name: 'foo' })
    .then(handleStringResponse)
    .catch(handleError);
axios.request<User, string>({
  method: 'get',
  url: '/user?id=12345'
})
    .then(handleStringResponse)
    .catch(handleError);
const instance1: axios.AxiosInstance = axios.create();
const instance2: axios.AxiosInstance = axios.create(config);
instance1(config)
    .then(handleResponse)
    .catch(handleError);
instance1.request(config)
    .then(handleResponse)
    .catch(handleError);
instance1.get('/user?id=12345')