The example available in our docs https://docs.openshift.com/container-platform/4.16/virt/vm_networking/virt-connecting-vm-to-linux-bridge.html#virt-creating-linux-bridge-nad-cli_virt-connecting-vm-to-linux-bridge is incorrect.

4.14+ for the multiline string
4.16+ for the boolean

Docs

1. Go to https://docs.openshift.com/container-platform/4.16/virt/vm_networking/virt-connecting-vm-to-linux-bridge.html#virt-creating-linux-bridge-nad-cli_virt-connecting-vm-to-linux-bridge
2. "Creating a Linux bridge NAD by using the command line" example

apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: bridge-network 
  annotations:
    k8s.v1.cni.cncf.io/resourceName: bridge.network.kubevirt.io/bridge-interface 
spec:
  config: '{
    "cniVersion": "0.3.1",
    "name": "bridge-network", 
    "type": "cnv-bridge", 
    "bridge": "bridge-interface", 
    "macspoofchk": false, 
    "vlan": 100, 
    "disableContainerInterface": "true",
    "preserveDefaultVlan": false 
  }'

apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: bridge-network 
  annotations:
    k8s.v1.cni.cncf.io/resourceName: bridge.network.kubevirt.io/bridge-interface 
spec:
  config: | # <<< CHANGED
    {
      "cniVersion": "0.3.1",
      "name": "bridge-network", 
      "type": "cnv-bridge", 
      "bridge": "bridge-interface", 
      "macspoofchk": false, 
      "vlan": 100, 
      "disableContainerInterface": true, # <<< CHANGED
      "preserveDefaultVlan": false 
    }   # <<< CHANGED

The existing snippet is not using a valid YAML for multiline string - try pasting it to https://www.yamllint.com/.
The "disableContainerInterface" should be a boolean https://github.com/containernetworking/plugins/blob/fec2d62676cbe4f2fd587b4840c7fc021bead3f9/plugins/main/bridge/bridge.go#L63.