proxy setting under WebDriver capabilities doesn't work

#### What are you trying to achieve?
set proxy for WebDriver helper

#### What do you get instead?
proxy setting under WebDriver capabilities doesn't work.

```bash

```

### Details

* CodeceptJS version: v3.0.0
* NodeJS Version: v14.13.1
* Operating System: Windows 10
* Configuration file:

```js
helpers: {
WebDriver: {
url: process.env.BASE_URL,
browser: process.env.BROWSER || 'chrome',
capabilities: {
proxy: {
"proxyType": "manual",
"httpProxy": "http://myproxyurl:3128/",
"sslProxy": "http://myproxyurl:3128/",
//"socksUsername": "codeceptjs",
//"socksPassword": "secret",
"noProxy": "bs-local.com"
}
}
}
},
```

從 WebDriver helper 對 capabilities 設定的處理著手，並使用提供的 Proxy 值在 CodeceptJS v3.0.0 上重現報告中的設定。確認 Proxy 是否到達 WebDriver 工作階段；完成的條件是，設定的 HTTP 和 SSL Proxy 設定會在 helper 啟動時套用。

由索引模型根據 Issue 內容生成。