openssl_free_key() is deprecated in PHP8

[stronk7]

From the php80 release notes:

. The openssl_x509_free() function is deprecated and no longer has an effect,
instead the OpenSSLCertificate instance is automatically destroyed if it is no
longer referenced.
. The openssl_pkey_free() (and its alias openssl_free_key)
function is deprecated and no longer has an effect,
instead the OpenSSLAsymmetricKey instance is automatically destroyed if it is no
longer referenced.

And there is a case of openssl_free_key() @ S3.php

Maybe it should be replaced to something like:

if (PHP_MAJOR_VERSION < 8) {
    openssl_free_key(self::$__signingKeyResource);
}
self::$__signingKeyResource = null;

Ciao :-)