Deprecated function: Function openssl_free_key()

This issue has arisen since the move to PHP 8.1:

Deprecated function: Function openssl_free_key() is deprecated in raven_signature_check() (line 381 of /var/aegir/platforms/drupal-7-2.9-staging/profiles/cambridge/modules/contrib/raven/raven.module).

This Stack Overflow article suggests that using the function may no longer be needed - https://stackoverflow.com/questions/69559775/php-openssl-free-key-deprecated.

The PHP manual also suggests it is no longer needed - https://www.php.net/manual/en/function.openssl-free-key.php

The code needs checking / tidying.