Switch Quilt and Purpur to image helper (#2229)

tests/setuponlytests/modrinth/docker-compose.yml

@@ -7,10 +7,7 @@ services:
       EULA: "true"
       SETUP_ONLY: "true"
       TYPE: FABRIC
-      FABRIC_LAUNCHER: /servers/fake.jar
-      CUSTOM_SERVER: /servers/fake.jar
       VERSION: 1.19.1
       MODRINTH_PROJECTS: fabric-api,cloth-config
     volumes:
       - ./data:/data
-      - ./fake.jar:/servers/fake.jar