Fix documentation regarding KMAC sizes

As per recommendation by jfinkhaeuser, this documents the defaults for
KMAC-128 as 32 and for KMAC-256 as 64. The code already accomodates for
these values, so no changes are needed there.

Fixes #22381

CLA: trivial

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from #22614)

doc/man7/EVP_MAC-KMAC.pod

@@ -51,7 +51,7 @@ It is an optional value with a length of at most 512 bytes, and is empty by defa
 =item "size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer>
 
 Sets the MAC size.
-By default, it is 16 for C<KMAC-128> and 32 for C<KMAC-256>.
+By default, it is 32 for C<KMAC-128> and 64 for C<KMAC-256>.
 
 =item "block-size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer>