Bug 1767951

The current docs read:

```

Verify the configuration:

$ curl -v -k -X OPTIONS \
"<cluster_url>/apis/migration.openshift.io/v1alpha1/namespaces/openshift-migration/migclusters" \ 
-H "Access-Control-Request-Method: GET" \
-H "Access-Control-Request-Headers: authorization" \
-H "Origin: https://<CAM_tool_url>" 

	Update the source cluster URL.
	Update the CAM tool URL.

The output appears similar to the following:

< HTTP/2 204
< access-control-allow-credentials: true
< access-control-allow-headers: Content-Type, Content-Length, Accept-Encoding, X-CSRF-Token, Authorization, X-Requested-With, If-Modified-Since
< access-control-allow-methods: POST, GET, OPTIONS, PUT, DELETE, PATCH
< access-control-allow-origin: https://migration-openshift-migration.apps.cluster
< access-control-expose-headers: Date
< cache-control: no-store
```

To be more specific "CAM tool URL" could be updated to read the "CAM UI URL". Would also be good to add an example to this note. So it could read:

```
Update with the CAM UI URL. This should be the URL used to access the CAM UI. For example:

-H "Origin: https://migration-openshift-migration.apps.cluster"
```