cdc: add compatibility notes for sort-dir (#6086)#6096

ti-chi-bot merged 4 commits into

pingcap:release-5.1pingcap/docs:release-5.1from

ti-chi-bot:cherry-pick-6086-to-release-5.1ti-chi-bot/docs:cherry-pick-6086-to-release-5.1Copy head branch name to clipboard