Use MySQL 9 in docker-compose.yml

[vvakame]

I got an error when execute make test in my local env with make start.

--- FAIL: TestValidSchema (0.19s)
    --- FAIL: TestValidSchema/endtoend-testdata/mysql_vector/mysql/sqlc.json-0 (0.02s)
        ddl_test.go:56: CREATE TABLE foo(
                id INT PRIMARY KEY auto_increment,
                embedding VECTOR(4)
            );: Error 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'VECTOR(4)
            )' at line 3

I am not familiar with MySQL, but from what I've researched, VECTOR data type appears to be supported from version 9 ¹.
sqlc's CI workflow uses version 9 too ².

Footnotes

1. https://dev.mysql.com/doc/relnotes/mysql/9.0/en/news-9-0-0.html#mysqld-9-0-0-vectors ↩

2. https://github.com/sqlc-dev/sqlc/blob/v1.29.0/.github/workflows/ci.yml#L64 ↩