Fix #66942: openssl_seal() memory leak

Related to the bug https://bugs.php.net/bug.php?id=66942 I reported a couple of days ago.

A similar memory leak in open_encrypt()  (https://bugs.php.net/bug.php?id=54060) has been fixed by calling EVP_CIPHER_CTX_cleanup() once.  But here we need to call it twice because the variable ctx is reused.