### Describe the issue

I set `axios.defaults.headers.common['Content-Type'] = 'application/json'`. When firing a `axios.patch` request (without a config), the request uses `application/x-www-form-urlencoded` instead.

### Example Code

```js
// This does not work as expected:
axios.defaults.headers.common['Content-Type'] = 'application/json'

// This does:
axios.defaults.headers.common['Content-Type'] = 'application/json'
axios.defaults.headers.patch['Content-Type'] = 'application/json'
```


### Expected behavior

I expected POST requests to use `axios.defaults.headers.common`, too.

I think this is where the problem (or intended behaviour) comes from: https://github.com/axios/axios/blob/3f53eb6960f05a1f88409c4b731a40de595cb825/lib/core/dispatchRequest.js#L46

### Axios Version

1.4.0

### Adapter Version

_No response_

### Browser

Firefox

### Browser Version

116.0.3 (64-bit)

### Node.js Version

_No response_

### OS

_No response_

### Additional Library Versions

_No response_

### Additional context/Screenshots

_No response_
test/specs/defaults.spec.js
});
    const payload = {x: 1};
    const transformed = defaults.transformRequest[0](payload, headers);
    expect(transformed).toEqual(jasmine.any(FormData));
  });
  it('should do nothing to request string', function () {
    expect(defaults.transformRequest[0]('foo=bar', new AxiosHeaders())).toEqual('foo=bar');
  });
  it('should transform response json', function () {
    const data = defaults.transformResponse[0].call(defaults, '{"foo":"bar"}');
    expect(typeof data).toEqual('object');
    expect(data.foo).toEqual('bar');
  });
  it('should do nothing to response string', function () {
    expect(defaults.transformResponse[0]('foo=bar')).toEqual('foo=bar');
  });
  it('should use global defaults config', function (done) {
    axios('/foo');
    getAjaxRequest().then(function (request) {
      expect(request.url).toBe('/foo');
      done();
    });
  });
  it('should use modified defaults config', function (done) {
    axios.defaults.baseURL = 'http://example.com/';
    axios('/foo');
    getAjaxRequest().then(function (request) {
      expect(request.url).toBe('http://example.com/foo');
      done();
    });