config controller delete command is inaccurate in clean-up / delete section

in section on deleting/recreating and re-acquiring the deployed resources - there is a typo in the anthos delete command
https://github.com/GoogleCloudPlatform/pubsec-declarative-toolkit/blob/main/docs/landing-zone-v2/README.md#clean-up

from
```
gcloud anthos config controller instance-name --location instance-region
in

if you want the deployed resources to live on and just destroy the Config Controller instance you can do so by running gcloud anthos config controller instance-name --location instance-region.
```

to
```
gcloud anthos config controller delete --location instance-region instance-name
in

if you want the deployed resources to live on and just destroy the Config Controller instance you can do so by running gcloud anthos config controller delete --location instance-region instance-name
```

see testing in https://github.com/GoogleCloudPlatform/pubsec-declarative-toolkit/issues/794
and documentation in
https://github.com/GoogleCloudPlatform/pubsec-declarative-toolkit/wiki/DevOps#scenarios

see
https://cloud.google.com/anthos-config-management/docs/how-to/config-controller-setup#delete
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