bug(MultiSelect): 在分组模式下内部 `Divider` 组件重叠

[AiYuZhen]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

官网测试地址：https://www.blazor.zone/multi-select#Group
在使用 GroupName 分组时，每个分组会在开始、结束添加 Divider 组件，导致前分组与下一分组的 Divider 组件重叠。

Expected Behavior

只保留起始位置的 Divider 组件或者将两个 Divider 重叠的分开一定的间隔。

Interactive render mode

Interactive Server (Interactive server-side rendering (interactive SSR) using Blazor Server)

Steps To Reproduce

参考官网例子：https://www.blazor.zone/multi-select#Group

Exceptions (if any)

No response

.NET Version

NET9.0

Anything else?

No response

[bb-auto]

@AiYuZhen Thank you for filing this issue. In order for us to investigate this issue, please provide a minimalistic repro project that illustrates the problem.

[Tony-ST0754]

你都看到问题在哪，也不顺手PR下