doc: Fix KDF example for scrypt

CLA: trivial
Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NPaul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17745)

doc/man1/openssl-kdf.pod.in

@@ -166,7 +166,7 @@ Use PBKDF2 to create a hex-encoded derived key from a password and salt:
 Use scrypt to create a hex-encoded derived key from a password and salt:
 
     openssl kdf -keylen 64 -kdfopt pass:password -kdfopt salt:NaCl \
-                -kdfopt N:1024 -kdfopt r:8 -kdfopt p:16 \
+                -kdfopt n:1024 -kdfopt r:8 -kdfopt p:16 \
                 -kdfopt maxmem_bytes:10485760 SCRYPT
 
 =head1 NOTES