[terraform-ibm-icd-postgresql] Update wording in fscloud related documentation #574
Description
ICD Postgres is FSCloud validated, so we should reword what we have documented in:
- https://github.com/terraform-ibm-modules/terraform-ibm-icd-postgresql/blob/main/modules/fscloud/README.md
- https://github.com/terraform-ibm-modules/terraform-ibm-icd-postgresql/tree/main/examples/fscloud
(Should be consistent with the wording in terraform-ibm-modules/terraform-ibm-icd-mongodb#476)