test/openssl/test_ssl: adjust certificate expiry date

test_connect_certificate_verify_failed_exception_message occasionally
fails. Is it possible that OpenSSL sees a different clock from Ruby by
more than 10 seconds?

http://ci.rvm.jp/logfiles/brlog.trunk-random0.20211111-072828

Let's give more time after the certificate expiration date to see if
this fixes the flakiness. We had similar occasional failures in
test_x509store.rb before, which disappeared after ruby/ruby commit
7930a352a5 and ruby/openssl commit fb2fcbb13734.

test/openssl/test_ssl.rb

@@ -1002,8 +1002,9 @@ class OpenSSL::TestSSL < OpenSSL::SSLTestCase
     }
 
     ctx_proc = proc { |ctx|
+      now = Time.now
       ctx.cert = issue_cert(@svr, @svr_key, 30, [], @ca_cert, @ca_key,
-                            not_before: Time.now-100, not_after: Time.now-10)
+                            not_before: now - 7200, not_after: now - 3600)
     }
     start_server(ignore_listener_error: true, ctx_proc: ctx_proc) { |port|
       store = OpenSSL::X509::Store.new