tls: remove SecureContext setFreeListLength
This function was introduced in 2684c902 as an internal helper function. The C++ implementation became a no-op in a57e2f21 when building against OpenSSL 1.1.0 (instead of OpenSSL 1.0.2), and eventually became a no-op in all supported OpenSSL versions in 970ce14f. Finally, eb204474 removed the only call site of setFreeListLength
(which was already a no-op at that point).
Refs: https://github.com/nodejs/node/pull/1529 Refs: https://github.com/nodejs/node/pull/10859 Refs: https://github.com/nodejs/node/pull/19794 Refs: https://github.com/nodejs/node/pull/38116