dm: add LOCK TABLES privilege note for managed MySQL sources#21467

ti-chi-bot[bot] merged 2 commits intopingcap:masterpingcap/docs-cn:masterfrom

qiancai:translate/fix/dm-lock-tables-managed-mysqlqiancai/docs-cn:translate/fix/dm-lock-tables-managed-mysqlCopy head branch name to clipboard