Honor precondition of UpdateStandardCursor() (dotnet#2172)

This CL reverts the logic to before
ff35bea - This is the April 2024 Update (v2.21.0) (dotnet#2115)

This fixes dotnet#2169.

src/Input/Silk.NET.Input.Glfw/GlfwCursor.cs

@@ -80,8 +80,8 @@ public StandardCursor StandardCursor
  {
  if (_standardCursor != value)
  {
- UpdateStandardCursor();
  _standardCursor = value;
+ UpdateStandardCursor();
  }
  }
  }