crypto: upgrade pbkdf2 without digest to an error

Commit a1163582 added a deprecation warning when pbkdf2 was called without an
explicit `digest` argument. This was because the default digest is `sha1`,
which is not-recommended from a security point of view. This upgrades it
to a runtime error when `digest` is undefined per the plan discussed in
the original issue.

Ref: https://github.com/nodejs/node/commit/a1163582c53dc6e00f3680084269600913b1cad2

PR-URL: https://github.com/nodejs/node/pull/11305


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>