Update to docker compose v2 (CTFd#2517)

Co-authored-by: Claire Goeckner-Wald <4743638-cgoecknerwald@users.noreply.gitlab.com>

Author: cgoecknerwald

README.md

@@ -52,7 +52,7 @@ You can use the auto-generated Docker images with the following command:
 
 Or you can use Docker Compose with the following command from the source repository:
 
-`docker-compose up`
+`docker compose up`
 
 Check out the [CTFd docs](https://docs.ctfd.io/) for [deployment options](https://docs.ctfd.io/docs/deployment/installation) and the [Getting Started](https://docs.ctfd.io/tutorials/getting-started/) guide