utils: Fix list_unmtainained_refs

There was a stray goto out that caused it to only look at the first
element in the system dirs list.

(cherry picked from commit e1e27559d1)

common/flatpak-utils.c

@@ -1058,8 +1058,6 @@ flatpak_list_unmaintained_refs (const char   *name_prefix,
               /* Reference found in at least one of the system installations */
               break;
             }
-
-          goto out;
         }
     }