fix: Deselect all has no effect in multiple mode if all rows are selected manually in DataGrid's SelectColumn

[Thoronion]

🐛 Bug Report

If a DataGrid's SelectColumn is set to Multiple. Selecting all rows manually or programmatically and then deselecting all by clicking the SelectAll checkbox has no effect. All the rows are still checked. Clicking a second time deselects all rows.

💻 Repro or Code Sample

1. Go to https://www.fluentui-blazor.net/datagrid-multi-select
2. Select Multiple mode.
3. Select all rows manually.
4. Deselect all rows by unchecking the SelectAll checkbox.
5. All rows are still selected.

🤔 Expected Behavior

All rows should be deselected on the first click.

😯 Current Behavior

The rows stays selected. Clicking a second time deselects all rows.

💁 Possible Solution

🔦 Context

🌍 Your Environment

• OS & Device: Windows
• Browser: Microsoft Edge, Google Chrome
• .NET 10.0.0-preview.3.25171.5 and Fluent UI Blazor library Version 4.11.9