system-variables: add documents for error_count and max_connections (#10525)#10656

ti-chi-bot merged 2 commits into

pingcap:release-5.3pingcap/docs:release-5.3from

ti-chi-bot:cherry-pick-10525-to-release-5.3ti-chi-bot/docs:cherry-pick-10525-to-release-5.3Copy head branch name to clipboard