[3.13] Clarify that dklen is expected in bytes for the hashlib functi…

…ons (GH-106624) (GH-119383)

(cherry picked from commit 5adf78f)

Co-authored-by: Mathijs Mortimer <thiezn@users.noreply.github.com>

Doc/library/hashlib.rst

@@ -328,7 +328,7 @@ include a `salt <https://en.wikipedia.org/wiki/Salt_%28cryptography%29>`_.
    your application, read *Appendix A.2.2* of NIST-SP-800-132_. The answers
    on the `stackexchange pbkdf2 iterations question`_ explain in detail.
 
-   *dklen* is the length of the derived key. If *dklen* is ``None`` then the
+   *dklen* is the length of the derived key in bytes. If *dklen* is ``None`` then the
    digest size of the hash algorithm *hash_name* is used, e.g. 64 for SHA-512.
 
    >>> from hashlib import pbkdf2_hmac
@@ -357,7 +357,7 @@ include a `salt <https://en.wikipedia.org/wiki/Salt_%28cryptography%29>`_.
 
    *n* is the CPU/Memory cost factor, *r* the block size, *p* parallelization
    factor and *maxmem* limits memory (OpenSSL 1.1.0 defaults to 32 MiB).
-   *dklen* is the length of the derived key.
+   *dklen* is the length of the derived key in bytes.
 
    .. versionadded:: 3.6