remove sigdata and optdata files (dotnet#9852)

Author: KevinRansom

src/fsharp/FSharp.Core/FSharp.Core.nuspec

@@ -11,8 +11,6 @@
         $CommonFileElements$
 
         <file src="FSharp.Core\$Configuration$\netstandard2.0\FSharp.Core.dll"              target="lib\netstandard2.0" />
-        <file src="FSharp.Core\$Configuration$\netstandard2.0\FSharp.Core.sigdata"          target="lib\netstandard2.0" />
-        <file src="FSharp.Core\$Configuration$\netstandard2.0\FSharp.Core.optdata"          target="lib\netstandard2.0" />
         <file src="FSharp.Core\$Configuration$\netstandard2.0\FSharp.Core.xml"              target="lib\netstandard2.0" />
 
         <!-- resources -->