Set maximum number of container instances for Google Cloud Run

I’m trying to set a maximum for containers Cloud Run can start (like so: Setting a maximum number of container instances).
I’m unable to find the right syntax in the terraform configuration file for Google.
I would have expected something like this but that’s wrong (only memory and cpu are allowed keys here):

 limits = {
        memory        = "1Gi"
        max_instances = 3

I’d be glad about a hint.