Use MySQL 9 in docker-compose.yml (#3944)

Author: vvakame

docker-compose.yml

@@ -1,7 +1,7 @@
 version: "3.8"
 services:
   mysql:
-    image: "mysql/mysql-server:8.0"
+    image: "mysql:9"
     ports:
       - "3306:3306"
     restart: always