R: delete dead code path

Author: jonsequitur

src/System.CommandLine/ArgumentArity.cs

@@ -116,12 +116,6 @@ internal static IArgumentArity Default(Type type, Argument argument, ISymbolSet
                 return ZeroOrOne;
             }
 
-            if (type == typeof(void))
-            {
-                // FIX: (Default) delete
-                return Zero;
-            }
-
             var parent = parents.Count > 0 ? parents[0] : default;
 
             if (typeof(IEnumerable).IsAssignableFrom(type) &&