Bump up the minimum required MySQL version (#25465)

MySQL 5.7 is at end of life.

https://mattermost.atlassian.net/browse/MM-55589

```release-note
We bump up minimum MySQL version to be 8.0.0
```


Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Ibrahim Serdar Acikgoz <serdaracikgoz86@gmail.com>

server/build/docker-compose.common.yml

@@ -1,7 +1,7 @@
 version: '2.4'
 services:
   mysql:
-    image: "mysql/mysql-server:5.7.12"
+    image: "mysql/mysql-server:8.0.32"
     restart: always
     networks:
       - mm-test
@@ -19,7 +19,7 @@ services:
     volumes:
       - ./docker/mysql.conf.d/source.cnf:/etc/mysql/conf.d/mysql.cnf
   mysql-read-replica:
-    image: "mysql/mysql-server:5.7.12"
+    image: "mysql/mysql-server:8.0.32"
     restart: always
     networks:
       - mm-test