https://learn.microsoft.com/ja-jp/dotnet/api/system.windows.forms.datagridviewrowcollection.removeat?view=netframework-4.8.1&viewFallbackFrom=windowsdesktop-6.0
DataGridViewRowCollection.RemoveAt(Int32) Method (System.Windows.Forms) | Microsoft Learn
Removes the row at the specified position from the collection.
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