Update phrasing from "Collaborator" to "Member" everywhere

[bnb]

Was reviewing CONTRIBUTING.md as a part of creating a new Contributing guide, and I noticed that the word "Collaborator" was still being used - instead of "Member" (ref: #49).

Here are the two documents where this word is still in place:

• CONTRIBUTING.md
• COLLABORATOR_GUIDE.md

If the Community Committee has moved away from the idea of a "Collaborator", these should probably be updated 🤔

[nebrius]

Collaborators and members are different things and we need to keep references to both. Perhaps we need to clarify that in the docs?

[dshaw]

@bnb: Is this issue still valid? Reviewing https://github.com/nodejs/community-committee/blob/master/CONTRIBUTING.md for https://github.com/nodejs/user-feedback, it appears these files have been significantly updated.

[bnb]

@dshaw I brought this up recently somewhere, though I can't find - as far as I can tell we've effectively not used the "Collaborator" role. I'll likely end up bringing this up as an agenda item to discuss, but for now this issue can be closed.