doc,crypto: cleanup removed pbkdf2 behaviours

PR-URL: #44733
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Akhil Marsonya <akhil.marsonya27@gmail.com>

doc/api/crypto.md

@@ -4309,9 +4309,6 @@ otherwise `err` will be `null`. By default, the successfully generated
 `derivedKey` will be passed to the callback as a [`Buffer`][]. An error will be
 thrown if any of the input arguments specify invalid values or types.
 
-If `digest` is `null`, `'sha1'` will be used. This behavior is deprecated,
-please specify a `digest` explicitly.
-
 The `iterations` argument must be a number set as high as possible. The
 higher the number of iterations, the more secure the derived key will be,
 but will take a longer amount of time to complete.
@@ -4407,9 +4404,6 @@ applied to derive a key of the requested byte length (`keylen`) from the
 If an error occurs an `Error` will be thrown, otherwise the derived key will be
 returned as a [`Buffer`][].
 
-If `digest` is `null`, `'sha1'` will be used. This behavior is deprecated,
-please specify a `digest` explicitly.
-
 The `iterations` argument must be a number set as high as possible. The
 higher the number of iterations, the more secure the derived key will be,
 but will take a longer amount of time to complete.