Fix bug.

lib/process_shared/posix/semaphore.rb

@@ -46,8 +46,8 @@ module ProcessShared
       # +shm_unlink+ on +sem+.
       #
       # @return [Proc] a finalizer
-      def self.make_finalizer(sem)
-        proc { LibC.shm_unlink(sem) }
+      def self.make_finalizer(sem) # already called in SharedMemory
+        proc {}
       end
 
       # Create a new semaphore with initial value +value+.  After