Remove `DELAY` var/functionality from examples/sandboxes `verify.sh`

Adding this was probably the worst design decision when creating the sandboxes - mostly it was added so you could see the proper logs when the sandbox had started 8/

Ideally the compositions use proper health checks and come up by themselves, but where that is not implemented or possible we can use the `wait_for` function to wait until something is ready

Once remaining sandboxes have been purged of this we should remove the functionality altogether