Add the 5.0 branch info to CONTRIBUTING.md (#5395)#5397

ti-chi-bot merged 2 commits into

pingcap:release-3.0pingcap/docs:release-3.0from

ti-srebot:release-3.0-e45daf58a747ti-srebot/docs:release-3.0-e45daf58a747Copy head branch name to clipboard