FreeType <= 2.6.1 on OSM rendering server causes Noto CJK too much bold

#2349 , #2391 Followup.

As the patch that enabled Noto CJK on Standard layer is up, I wrote this issue.

Take Tokyo, Japan for example, you can see the CJK fonts is way too bold compared to ref numbers:

IMHO we can use lighter variant of Noto CJK for both regular and bold font.
My personal suggestion:

Noto Sans CJK Regular -> Noto Sans CJK DemiLight

Noto Sans CJK Bold -> Noto Sans CJK Medium

The following is a screenshot I made to compare the font weight:

But actual Mapnik rendering may be compared too. Can someone do it in Tokyo, Seoul and Taipei?

FreeType <= 2.6.1 on OSM rendering server causes Noto CJK too much bold #2402