### Describe the bug

The following test code in `AxiosHeaders.js`

```
  describe('clear', ()=> {
    it('should clear all headers', () => {
      const headers = new AxiosHeaders({x: 1, y:2});

      headers.clear();

      assert.notDeepStrictEqual(headers, {});
    });

    it('should clear matching headers if a matcher was specified', () => {
      const headers = new AxiosHeaders({foo: 1, 'x-foo': 2, bar: 3});

      assert.notDeepStrictEqual(headers, {foo: 1, 'x-foo': 2, bar: 3});

      headers.clear(/^x-/);

      assert.notDeepStrictEqual(headers, {foo: 1, bar: 3});
    });
  });
```

Doesn't fail if you remove the implementation for `headers.clear()`

### To Reproduce

Remove the following lines

```
  clear(matcher) {
    const keys = Object.keys(this);
    let i = keys.length;
    let deleted = false;

    while (i--) {
      const key = keys[i];
      if(!matcher || matchHeaderValue(this, this[key], key, matcher)) {
        delete this[key];
        deleted = true;
      }
    }

    return deleted;
  }
```

to 

```
  clear(matcher) {
    return true;
  }
```

### Code snippet

_No response_

### Expected behavior

Tests should fail

### Axios Version

_No response_

### Adapter Version

_No response_

### Browser

_No response_

### Browser Version

_No response_

### Node.js Version

_No response_

### OS

_No response_

### Additional Library Versions

_No response_

### Additional context/Screenshots

_No response_
lib/core/AxiosHeaders.js
if (utils.isFunction(filter)) {
    return filter.call(this, value, header);
  }
  if (!utils.isString(value)) return;
  if (utils.isString(filter)) {
    return value.indexOf(filter) !== -1;
  }
  if (utils.isRegExp(filter)) {
    return filter.test(value);
  }
}
function formatHeader(header) {
  return header.trim()
    .toLowerCase().replace(/([a-z\d])(\w*)/g, (w, char, str) => {
      return char.toUpperCase() + str;
    });
}
function buildAccessors(obj, header) {
  const accessorName = utils.toCamelCase(' ' + header);
  ['get', 'set', 'has'].forEach(methodName => {
    Object.defineProperty(obj, methodName + accessorName, {
      value: function(arg1, arg2, arg3) {
        return this[methodName].call(this, header, arg1, arg2, arg3);
      },
      configurable: true
    });
  });
}
class AxiosHeaders {