Don't add root to any group

This was introduced in 5989ec37de, and
probably that was not the intention.

Adding root to groups doesn't break anything, but I don't think it makes
any sense either.

kali-config/common/includes.installer/kali-finish-install

@@ -64,7 +64,7 @@ configure_usergroups() {
     # wireshark - capture sessions in wireshark
     kali_groups="adm,kaboxer,dialout,wireshark"
 
-    for user in $(get_user_list); do
+    for user in $(get_user_list | grep -xv root); do
 	echo "INFO: adding user '$user' to groups '$kali_groups'"
 	usermod -a -G "$kali_groups" $user || true
     done