[3.0][docs] fix mysql pipeline connector option in readme (#2834)

Author: Shawn-Hx

README.md

@@ -45,7 +45,7 @@ source:
   port: 3306
   username: admin
   password: pass
-  table: db0.commodity, db1.user_table_[0-9]+, [app|web]_order_\.*
+  tables: db0.commodity, db1.user_table_[0-9]+, [app|web]_order_\.*
 
 sink:
   type: doris