crypto: remove deprecated legacy API

The `crypto.Credentials` legacy API has been Runtime deprecated since
v0.11.13 and users had been adviced to use `tls.SecureContext` instead.

PR-URL: https://github.com/nodejs/node/pull/21153
Fixes: https://github.com/nodejs/node/issues/20793


Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>