Update custom-domain.yaml environment

The description for some of these parameters changed and the
environment needs to be updated to reflect that.

Change-Id: Ia0a617910e2d6effcf00bdf20cba6b38b7722844

environments/predictable-placement/custom-domain.yaml

@@ -21,7 +21,7 @@ parameter_defaults:
   # Type: string
   CloudNameCtlplane: overcloud.ctlplane.localdomain
 
-  # The DNS name of this cloud's internal API endpoint. E.g. 'ci-overcloud.internalapi.tripleo.org'.
+  # The DNS name of this cloud's internal_api endpoint. E.g. 'ci-overcloud.internalapi.tripleo.org'.
   # Type: string
   CloudNameInternal: overcloud.internalapi.localdomain
 
@@ -29,7 +29,7 @@ parameter_defaults:
   # Type: string
   CloudNameStorage: overcloud.storage.localdomain
 
-  # The DNS name of this cloud's storage management endpoint. E.g. 'ci-overcloud.storagemgmt.tripleo.org'.
+  # The DNS name of this cloud's storage_mgmt endpoint. E.g. 'ci-overcloud.storagemgmt.tripleo.org'.
   # Type: string
   CloudNameStorageManagement: overcloud.storagemgmt.localdomain