pem_password_cb(3): References to other man pages

Refer to OSSL_ENCODER_to_bio and OSSL_DECODER_from_bio man pages.

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18164)
diff --git a/doc/man3/PEM_read_bio_PrivateKey.pod b/doc/man3/PEM_read_bio_PrivateKey.pod
index 27e7849..d84af65 100644
--- a/doc/man3/PEM_read_bio_PrivateKey.pod
+++ b/doc/man3/PEM_read_bio_PrivateKey.pod
@@ -193,8 +193,8 @@
 =head1 DESCRIPTION
 
 All of the functions described on this page that have a I<TYPE> of B<DH>, B<DSA>
-and B<RSA> are deprecated. Applications should use OSSL_ENCODER_to_bio() and
-OSSL_DECODER_from_bio() instead.
+and B<RSA> are deprecated. Applications should use L<OSSL_ENCODER_to_bio(3)> and
+L<OSSL_DECODER_from_bio(3)> instead.
 
 The PEM functions read or write structures in PEM format. In
 this sense PEM format is simply base64 encoded data surrounded