Fix games/cockatrice plist. With CMake 3.10, (also CMake 3.11, which is
why I noticed this) and Qt 5.9, there are translations that are not included
in the plist. Poudriere shows me:

====> Running Q/A tests (stage-qa)
====> Checking for pkg-plist issues (check-plist)
===> Parsing plist
===> Checking for items in STAGEDIR missing from pkg-plist
Error: Orphaned: %%DATADIR%%/translations/cockatrice_ca.qm
Error: Orphaned: %%DATADIR%%/translations/cockatrice_el.qm
<snip>

Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D14784