Add eatmydata to offline.downloads

This should fix:

    in-target: E: Unable to locate package eatmydata
    eatmydata-udeb/eatmydata-install: error: unable to find /usr/bin/eatmydata after installing the eatmydata package

Cf. 31fb818dec

simple-cdd/profiles/offline.downloads

@@ -1,3 +1,5 @@
+# Ensure eatmydata is available for eatmydata.udeb
+eatmydata
 # Add packages required for virtualization support (installed by
 # /usr/lib/finish-install.d/08hw-detect) including their recommends
 hyperv-daemons