Update conf for debian-cd 3.1.36

Otherwise we get plenty of error messages:

DEBUG build/debian-cd stderr: Use of uninitialized value
$ENV{"NONFREE_COMPONENTS"} in split at
<<DIR>>/simple-cdd/debian-cd/tools/which_deb line 23.

simple-cdd/simple-cdd.conf

@@ -88,6 +88,9 @@ export OMIT_DOC_TOOLS=1
 export DOJIGDO=0
 export NORECOMMENDS=0
 export NONFREE=1
+# Below: change to "non-free non-free-firmware" if ever Kali gets a
+# non-free-firmware component
+export NONFREE_COMPONENTS="non-free"
 export CONTRIB=1
 export FORCE_FIRMWARE=1
 export ARCHIVE_KEYRING_PACKAGE=kali-archive-keyring