DataGrid 全选按钮，设置 SelectionMode="Single" 不自动隐藏了

[yangzezhao-0405]

Describe the bug

1. 3.5版本中，只要设置 SelectionMode="Single" ，ShowSelectAllButton 就会自动隐藏；
2. 最新版本，将 ShowSelectAllButton 改为复选框后，失效了。

Steps to reproduce the bug

SelectionMode="Single"
hc:DataGridAttach.ShowSelectAllButton="False"

Expected behavior

No response

Screenshots

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NuGet package version

None

IDE

No response

Framework type

No response

Windows version

No response

Additional context

No response