Discrepancy between manual and channels.scm

[ison]

Under "6.7 Declaring Channel Dependencies" the examples show names being
quoted, such as (name 'some-collection) however this causes guix pull to
fail. I don't remember the exact error but it was failing the "match"
statement under "resolve-dependencies" in "guix/channels.scm".

(name "some-collection") also fails.
(name some-collection) succeeds, without any quoting.

I'm not sure if it's the manual which needs fixing or the code, but
specifying the name without quoting would be inconsistent with how
channel names are declared in ~/.config/guix/channels.scm.