securerandom: fix up r57384

SecureRandom.gen_random_openssl still refers to Random.raw_seed, which
is renamed to Random.urandom by r57384.  [Bug #9569]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57707 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/securerandom.rb

@@ -90,7 +90,7 @@ module SecureRandom
       unless @pid == pid
         now = Process.clock_gettime(Process::CLOCK_REALTIME, :nanosecond)
         OpenSSL::Random.random_add([now, @pid, pid].join(""), 0.0)
-        seed = Random.raw_seed(16)
+        seed = Random.urandom(16)
         if (seed)
           OpenSSL::Random.random_add(seed, 16)
         end