[ruby/openssl] Revert "Skip OpenSSL::TestHMAC#test_dup when running with RHEL9"

This reverts commit https://github.com/ruby/openssl/commit/9493d4a3bb26.

https://github.com/ruby/openssl/commit/b880a023dd

test/openssl/test_hmac.rb

@@ -21,9 +21,6 @@ class OpenSSL::TestHMAC < OpenSSL::TestCase
   end
 
   def test_dup
-    require "etc"
-    pend "[Bug #19386] OpenSSL 3.0.1 of RHEL9 is not working this test" if Etc.uname[:release] =~ /el9/
-
     h1 = OpenSSL::HMAC.new("KEY", "MD5")
     h1.update("DATA")
     h = h1.dup