[ruby/openssl] test/openssl/test_ocsp.rb: fix flaky test

Fixes: https://github.com/ruby/openssl/issues/695

https://github.com/ruby/openssl/commit/95281fe4a9

test/openssl/test_ocsp.rb

@@ -228,7 +228,7 @@ class OpenSSL::TestOCSP < OpenSSL::TestCase
     assert_equal OpenSSL::OCSP::V_CERTSTATUS_REVOKED, single.cert_status
     assert_equal OpenSSL::OCSP::REVOKED_STATUS_UNSPECIFIED, single.revocation_reason
     assert_equal now - 400, single.revocation_time
-    assert_in_delta (now - 301), single.this_update, 1
+    assert_in_delta (now - 300), single.this_update, 1
     assert_equal nil, single.next_update
     assert_equal [], single.extensions