表情判断逻辑仍有漏洞

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- The steps to reproduce.
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输入下面的格式就不会显示表情
```
表情:测试1 :smile:
```

建议增加一对符号来判断，双冒号太容易误判了。

例如：
```
[:smile:]
```
或者：
```
(:smile:)
```
