BUG: amis折叠器的手机效果错误

#### 描述问题：

在表单里的“折叠器”，手机效果不正确。（见截图 标示1）
不在表单里的“折叠器”，手机效果正确。（见截图 标示2）

另外，不在表单里的“折叠器”，多行文本底下有边框线，加上折叠器的边框线，就出现了2条边框线。

#### 截图或视频：

#### 如何复现（请务必完整填写下面内容）：

1. 你是如何使用 amis 的？
`sdk`

2. amis 版本是什么？请先在最新 beta 版本测试问题是否存在
amis v6.6有问题，之前版本也有问题。

4. 粘贴有问题的完整 `amis schema` 代码：
```
{
"type": "page",
"title": "Hello world",
"body": [
{
"type": "tpl",
"tpl": "初始页面",
"wrapperComponent": "",
"inline": false,
"id": "u:6b4d544c2b45"
},
{
"type": "input-month",
"label": "日期",
"name": "date",
"id": "u:60be6cc33828",
"displayFormat": "YYYY-MM",
"placeholder": "请选择月份",
"valueFormat": "X",
"minDate": "",
"maxDate": "",
"value": "${TODAY()}"
},
{
"id": "u:da2573af02a3",
"type": "form",
"title": "表单",
"mode": "inline",
"dsType": "api",
"feat": "Insert",
"body": [
{
"type": "input-text",
"label": "文本",
"name": "text",
"id": "u:b2923a6ec96b"
},
{
"type": "input-number",
"label": "数字",
"name": "number",
"keyboard": true,
"id": "u:e578e4e36339"
},
{
"type": "textarea",
"label": "多行文本",
"name": "textarea",
"id": "u:9f4764af1c67"
},
{
"type": "collapse-group",
"activeKey": [
"1"
],
"body": [
{
"type": "collapse",
"key": "1",
"active": true,
"header": "标题1",
"body": [
{
"type": "tpl",
"tpl": "这里是内容1",
"wrapperComponent": "",
"inline": false,
"id": "u:ee05a3c01a9b"
}
],
"id": "u:c982bb36835d"
},
{
"type": "collapse",
"key": "2",
"header": "标题2",
"body": [
{
"type": "tpl",
"tpl": "这里是内容1",
"wrapperComponent": "",
"inline": false,
"id": "u:2627bdd6946b"
}
],
"id": "u:904ef7430f3f"
}
],
"id": "u:f5ce22048efe"
}
],
"actions": [
{
"type": "button",
"label": "提交",
"onEvent": {
"click": {
"actions": [
{
"actionType": "submit",
"componentId": "u:da2573af02a3"
}
]
}
},
"level": "primary",
"id": "u:dc53c87ef8bd"
}
],
"resetAfterSubmit": true,
"wrapWithPanel": true
},
{
"type": "collapse-group",
"activeKey": [],
"body": [
{
"type": "collapse",
"key": "1",
"active": false,
"header": "标题1",
"body": [
{
"type": "tpl",
"tpl": "这里是内容1",
"wrapperComponent": "",
"inline": false,
"id": "u:08e47923071e"
}
],
"id": "u:5e2d1d0918a3",
"collapsable": true
},
{
"type": "collapse",
"key": "2",
"header": "标题2",
"body": [
{
"type": "tpl",
"tpl": "这里是内容1",
"wrapperComponent": "",
"inline": false,
"id": "u:153829acc75c"
},
{
"type": "textarea",
"label": "多行文本",
"name": "textarea",
"id": "u:fa48f8a10f34",
"minRows": 3,
"maxRows": 20,
"readOnly": false,
"static": true,
"value": "1\n1\n2"
}
],
"id": "u:8e569e72a511",
"active": false
},
{
"type": "tpl",
"tpl": "请编辑内容",
"inline": true,
"wrapperComponent": "",
"id": "u:812a0e9bc3f7"
}
],
"id": "u:67ae11ecb81f",
"accordion": false
}
],
"id": "u:09fbb140b7c7"
}
```

5. 操作步骤
手机浏览器查看网页

Start by reproducing the supplied AMIS schema in a mobile browser and compare the collapse-group rendered inside and outside the form. Check the collapse and textarea presentation in both cases; done means the form layout matches the standalone layout and the extra border beneath the multiline text is removed.

Written by the indexing model from the issue text.