Fix source only package issue in nuget

Misaki.HighPerformance.LowLevel/FunctionPointer.cs

@@ -1,40 +0,0 @@
-using System.Runtime.InteropServices;
-
-namespace Misaki.HighPerformance.LowLevel;
-
-/// <summary>
-/// A structure that encapsulates a function pointer and provides methods to convert between
-/// </summary>
-/// <remarks>
-/// This structure used marshalling to convert between function pointers and delegates, which is not ideal for high-performance scenarios.
-/// Use this only when necessary, and prefer using <c>delegate* unmanaged</c> for better performance.
-/// </remarks>
-/// <typeparam name="T">The delegate type that the function pointer represents.</typeparam>
-public readonly struct FunctionPointer<T>
-    where T : Delegate
-{
-    private readonly nint _ptr;
-
-    /// <summary>
-    /// Gets the native function pointer associated with this function pointer instance.
-    /// </summary>
-    public readonly nint Pointer => _ptr;
-
-    /// <summary>
-    /// Gets the delegate instance associated with the specified function pointer.
-    /// </summary>
-    /// <remarks>This property uses <see
-    /// cref="Marshal.GetDelegateForFunctionPointer{TDelegate}"/> to convert the function
-    /// pointer to a delegate. Ensure that the function pointer is valid and compatible with the delegate type
-    /// <typeparamref name="T"/>.</remarks>
-    public T Delegate => Marshal.GetDelegateForFunctionPointer<T>(_ptr);
-
-    /// <summary>
-    /// Creates a new instance of this function pointer with the following native pointer.
-    /// </summary>
-    /// <param name="ptr"></param>
-    public FunctionPointer(T func)
-    {
-        _ptr = Marshal.GetFunctionPointerForDelegate<T>(func);
-    }
-}