this.curl发起请求，无法带上自定义header

### Your detail info about the Bug:

如下是一个调用OpenAI api的controller，请求OpenAI API接口的时候，自定义header带不上。
const Controller = require('egg').Controller;

class OpenAIController extends Controller {
async completions() {
const param = this.ctx.request.body;
const apiUrl = `${this.config.openai.baseUrl}/completions`;
try {
const result = await this.ctx.curl(apiUrl, {
method: 'POST',
contentType: 'json',
headers: {
Authorization: `Bearer ${this.config.openai.apiKey}}`,
},
data: param,
streaming: param.stream,
dataType: 'json',
});
this.ctx.status = result.status;
this.ctx.set(result.header);
this.ctx.body = result.data;
} catch (error) {
this.ctx.status = 200;
this.ctx.body = { error: 'error' };
this.ctx.logger.info('OpenAI API call failed:', error);
}
}
}

module.exports = OpenAIController;

如下是抓包的结果：

从抓包的请求中可以看到，并没有自定义headers Authorization 这个请求头，这个是不符合预期的。

### Reproduction Repo

[归档.zip](https://github.com/eggjs/egg/files/12138656/default.zip)

### Node Version

V16.20.1

### Eggjs Version

3

### Plugin Name and its version

无

### Platform and its version

mac