Remove extra read_string for a string field

* `servent.s_name.type` is always `string` now.

Author: eregon

lib/truffle/socket/truffle/foreign/servent.rb

@@ -31,7 +31,7 @@ class Servent < Truffle::FFI::Struct
         config('platform.servent', :s_name, :s_aliases, :s_port, :s_proto)
 
         def name
-          self[:s_name].read_string
+          self[:s_name]
         end
 
         def port