cjdns: reduce password length to 32

Maximum password length per cjdns code is somehwhere less than that, see
ecd01e7681/client/AdminClient.c (L80)

Currently we generate 96 char long passwords that don't work

This changes it so password length is just 32 chars long

nixos/modules/services/networking/cjdns.nix

@@ -245,7 +245,7 @@ in
         fi
 
         if [ -z "$CJDNS_ADMIN_PASSWORD" ]; then
-            echo "CJDNS_ADMIN_PASSWORD=$(tr -dc A-Za-z0-9 </dev/urandom | head -c 96)" \
+            echo "CJDNS_ADMIN_PASSWORD=$(tr -dc A-Za-z0-9 </dev/urandom | head -c 32)" \
                 >> /etc/cjdns.keys
         fi
       '';