Remove deprecated `upvotes` and `downvotes` from the notes API

changelogs/unreleased/api-notes-entity-fields.yml

doc/api/notes.md

doc/api/projects.md

doc/api/users.md

doc/api/v3_to_v4.md

lib/api/api.rb

lib/api/entities.rb

lib/api/v3/entities.rb

lib/api/v3/notes.rb

lib/api/v3/projects.rb

lib/api/v3/users.rb

spec/requests/api/v3/notes_spec.rb

spec/requests/api/v3/users_spec.rb