app-text/a2ps: Revert from linguas_ja to cjk USE flag.

app-text/a2ps: Revert from linguas_ja to cjk USE flag.

The ebuild applies patches depending on the flag setting. However,
these are intrusive, as they change defaults in other locales too
(e.g., "tex" is changed to "ptex" in texi2dvia2ps). Therefore this
patching should neither depend on LINGUAS, nor on L10N, nor be done
unconditionally.

For now, change it to be conditional on the cjk flag, which was the
solution already used in a previous version of the ebuild.

Package-Manager: Portage-2.3.19, Repoman-2.3.6