Update editor draft URL-s for notes

[iherman]

The editors' drafts still referred to the epub33 folder on the repo, it shoud refer to wg-notes.

While I was at it:

• I added the <meta> for dark mode to all specs
• I commented out (where applicable) the reference to errata; it pointed to the epub33 but, for notes, there is no real need for the full errata management while the WG is active.

[iherman]

This is non-controversial editorial PR, I will merge it right away.