listchars were faded weirdly in some themes

[kevinhwang91]

Reproduce:

1. cat ~/mini.vim

call plug#begin('~/.config/nvim/plugged')
Plug 'TaDaa/vimade'
Plug 'joshdick/onedark.vim'
call plug#end()

set list
colorscheme onedark

2. nvim -u ~/mini.vim +'split defer-multi.go' defer.go

The chars of the faded window were brighter than the unfaded one.

[gzbd]

Iceberg theme is also affected by this issue

I would like to dim the listchars also.

I've tried to add SpecialKey and NonText to basegroups setting but it didn't work.

[ckangnz]

I can confirm that gruvbox is also affected. It's weird how it only affects certain SpecialKeys?