deps: update llhttp to 6.0.0
See: https://github.com/nodejs/node/pull/37678#issuecomment-821156758 See: https://github.com/nodejs/llhttp/releases/tag/release%2Fv6.0.0
cc @BethGriggs @nodejs/http
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
See: https://github.com/nodejs/node/pull/37678#issuecomment-821156758 See: https://github.com/nodejs/llhttp/releases/tag/release%2Fv6.0.0
cc @BethGriggs @nodejs/http