### 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/headers.spec.js
if (headers.hasOwnProperty(key)) {
          expect(request.requestHeaders[key]).toEqual(headers[key]);
        }
      }
      done();
    });
  });
  it('should add extra headers for post', function (done) {
    const headers = axios.defaults.headers.common;
    axios.post('/foo', 'fizz=buzz');
    getAjaxRequest().then(function (request) {
      for (const key in headers) {
        if (headers.hasOwnProperty(key)) {
          expect(request.requestHeaders[key]).toEqual(headers[key]);
        }
      }
      done();
    });
  });
  it('should reset headers by null or explicit undefined', function (done) {
    axios.create({
      headers: {
        common: {
          'x-header-a': 'a',
          'x-header-b': 'b',
          'x-header-c': 'c'
        }
      }
    }).post('/foo', {fizz: 'buzz'}, {
      headers: {