fix(docker): fix MySQL 5.7 definition in docker-compose

[jkomyno]

Before this PR, running

docker compose -f docker-compose.yml up --remove-orphans mysql-5-7

resulted in the mysql-5-7 container continuously restarting with the following error:

prisma-engines-mysql-5-7-1  | 2023-11-09 15:58:30+00:00 [ERROR] [Entrypoint]: MYSQL_USER="root", MYSQL_USER and MYSQL_PASSWORD are for configuring a regular user and cannot be used for the root user
prisma-engines-mysql-5-7-1  |     Remove MYSQL_USER="root" and use one of the following to control the root user password:
prisma-engines-mysql-5-7-1  |     - MYSQL_ROOT_PASSWORD
prisma-engines-mysql-5-7-1  |     - MYSQL_ALLOW_EMPTY_PASSWORD
prisma-engines-mysql-5-7-1  |     - MYSQL_RANDOM_ROOT_PASSWORD
prisma-engines-mysql-5-7-1 exited with code 1

This caused Schema Engine tests targeting MySQL 5.7 to fail in main.

Removing the MYSQL_USER: root env var from the docker-compose definition fixed the problem locally. Let's run this on the CI.

[janpio]

If this works and is needed, make sure to check all other @prisma repos - we probably copy/pasted that to other places.

[jkomyno]

If this works and is needed, make sure to check all other @prisma repos - we probably copy/pasted that to other places.

Neither prisma/prisma nor prisma/ecosystem-tests use mysql:5.7, so I think we don't need to modify any other repo.

[codspeed-hq]

CodSpeed Performance Report

Merging #4430 will not alter performance

_{Comparing fix/mysql-5.7 (45fefed) with main (2963919)}

Summary

✅ 11 untouched benchmarks