[css-lists] Grammar for counter names should be consistent.

[emilio]

https://drafts.csswg.org/css-lists-3/#funcdef-counter says:

counter( <ident>, [ <counter-style> | none ]? )
counters( <ident>, <string>, [ <counter-style> | none ]? )

However counter-increment and such say:

[ <custom-ident> <integer>? ]+ | none 

Looks like <ident> and <custom-ident> should be used consistently. I suspect we want to use <custom-ident> everywhere?

[fantasai]

Looks like this was fixed in cb834e9