Clarify which dicts are from Ubuntu

services/spelling/install_deps.sh

@@ -1,4 +1,6 @@
-# some spelling packages are missing from debian and are on ubuntulo
+# The following aspell packages exist in Ubuntu but not Debian:
+# aspell-af, aspell-id, aspell-nr, aspell-ns, aspell-ss, aspell-st, aspell-tn, 
+# aspell-ts, aspell-xh, aspell-zu
 echo "deb http://us.archive.ubuntu.com/ubuntu/ bionic main universe" >> /etc/apt/sources.list
 apt-key adv --no-tty --keyserver keyserver.ubuntu.com --recv-keys 3B4FE6ACC0B21F32
 apt-get update