[Fontconfig] How to delete "ja" lang from a specific font?

[Kenichi Handa]

I installed the font "WenQuanYi Zen Hei" by the debian
package "ttf-wqy-zenhei".  The font convers many Han glyphs
including Japanese specific ones. 

% fc-list 'WenQuanYi Zen Hei' lang

shows this list:

:lang=aa|af|ast|ava|ay|be|bg|bi|br|ca|ce|ch|co|da|de|el|en|es|eu|fj|fo|fr|fur|fy|gd|gl|gv|ho|ia|id|ie|ik|io|is|it|ja|ko|kum|lb|lez|mg|nb|nds|nl|nn|no|nr|ny|oc|om|os|pt|rm|ru|sel|sh|sm|sma|smj|so|sq|sr|ss|st|sv|sw|to|ts|vo|wa|wo|xh|yap|zh-cn|zh-hk|zh-mo|zh-sg|zh-tw|zu

But, as Japanese glyphs are not good, I'd like to remove
"ja" from that language list.  Could someone please tell me
how to write ~/.fonts.conf for that?

---
Kenichi Handa
handa at ni.aist.go.jp