Since we need this boot image bump to properly deliver the fix for the other `blocker+` BZ#2007089, I'm transitively applying the same flag here.

$ oc get clusterversion
NAME      VERSION                             AVAILABLE   PROGRESSING   SINCE   STATUS
version   4.9.0-0.nightly-2021-09-25-094414   True        False         18m     Cluster version is 4.9.0-0.nightly-2021-09-25-094414
$ oc -n openshift-machine-api get machinesets
NAME                                  DESIRED   CURRENT   READY   AVAILABLE   AGE
mnguyen49bi-bd7bk-worker-us-west-2a   1         1         1       1           36m
mnguyen49bi-bd7bk-worker-us-west-2b   1         1         1       1           36m
mnguyen49bi-bd7bk-worker-us-west-2c   1         1         1       1           36m
mnguyen49bi-bd7bk-worker-us-west-2d   0         0                             36m
$ oc -n openshift-machine-api get machinesets/mnguyen49bi-bd7bk-worker-us-west-2a -o yaml | grep ami
                f:ami: {}
          ami:
            id: ami-084fb1316cd1ed4cc


matches boot image PR
       "us-east-2": {
            "hvm": "ami-09e637fc5885c13cc"
        },
        "us-west-1": {
            "hvm": "ami-0fa0f6fce7e63dd26"
        },
        "us-west-2": {
            "hvm": "ami-084fb1316cd1ed4cc"
        }

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: OpenShift Container Platform 4.9.0 bug fix and security update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2021:3759