zsh: make autosuggest coloring a bit more subtle
zsh: make autosuggest coloring a bit more subtle

This is less "in your face", which I think I prefer. I don't want my
shell screaming at me "YOU PROBABLY WANT TO TYPE THIS THING THAT YOU'VE
TYPED IN THE PAST", but rather, nod in my direction with an implied "I'm
here if you need me".

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent