Call the :vm_set_class primitive in IO#reopen directly

* There are no other usages anymore.

Author: eregon

src/main/ruby/core/io.rb

@@ -2207,7 +2207,8 @@ def reopen(other, mode=undefined)
 
         Truffle::IOOperations.dup2_with_cloexec(io.fileno, @descriptor)
 
-        Truffle::Internal::Unsafe.set_class self, io.class
+        Truffle.invoke_primitive :vm_set_class, self, io.class
+
         if io.respond_to?(:path)
           @path = io.path
         end

src/main/ruby/core/truffle/internal.rb

@@ -35,19 +35,6 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 module Truffle::Internal
-
-  module Unsafe
-    def self.set_class(obj, cls)
-      Truffle.primitive :vm_set_class
-
-      if obj.kind_of? ImmediateValue
-        raise TypeError, 'Can not change the class of an immediate'
-      end
-
-      raise ArgumentError, "Class #{cls} is not compatible with #{obj.inspect}"
-    end
-  end
-
   def self.get_data(path, offset)
     file = File.open(path)
     file.seek(offset)