[css-scrollbars-1] Horizontal Review

[frivoal]

• A11y review self review, review requested, green light received
• I18n review self-review, review requested, green light received
• Privacy review self review, review requested, green light received
• Security review self review, review requested
• TAG review completed, green light recieved

[frivoal]

Considering the security review has having timed out, since we did not hear back after 3 months.

Everything else came back clear (with some discussion on a11y which we were able to resolve).

Closing.

[frivoal]

(minutes of the WG validating this: https://logs.csswg.org/irc.w3.org/css/2021-12-01/#e1449779)