Remove `ibm_iam_account_settings` from sample-deployable-architectures solution

[ocofaigh]

Stop using it here:

sample-deployable-architectures/solutions/tf-fullstack-da/main.tf

Line 82 in bfb0ae1

data "ibm_iam_account_settings" "iam_account_settings" {

Instead get the account ID output from COS modules (which is coming in terraform-ibm-modules/terraform-ibm-cos#742)

[imprateeksh]

The PR was merged and the changes are present as part of release v1.2.5.
Closing this issue.