gnu: 0ad-data: Make the package public but hidden.

So that ci.guix can pick it up (esp. the ‘disarchive’ and ‘source’ jobsets).

* gnu/packages/games.scm (0ad-data): Make variable public and add ‘hidden?’
property.

Reported-by: Ludovic Courtès <ludo@gnu.org>
Change-Id: I8129811f386a356a0e236850a43e6dee9bb6c3ac

gnu/packages/games.scm

@@ -7234,7 +7234,7 @@ fight against their plot and save his fellow rabbits from slavery.")
                    license:cc-by-sa3.0
                    license:cc-by-sa4.0))))
 
-(define 0ad-data
+(define-public 0ad-data
   (package
     (name "0ad-data")
     (version "0.0.26-alpha")
@@ -7270,6 +7270,7 @@ fight against their plot and save his fellow rabbits from slavery.")
     (synopsis "Data files for 0ad")
     (description "0ad-data provides the data files required by the game 0ad.")
     (home-page "https://play0ad.com")
+    (properties '((hidden? . #t)))
     (license (list (license:fsdg-compatible
                     "http://tavmjong.free.fr/FONTS/ArevCopyright.txt"
                     "Similar to the license of the Bitstream Vera fonts.")