Revert authorisation policy role migration

[kavya498]

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Relates OR Closes #0000

Output from acceptance testing:

=== RUN   TestAccIBMIAMAuthorizationPolicyDelegatorRole
2021/09/30 19:37:37 Configuring SoftLayer Session with API key
2021/09/30 19:37:37 Configuring IBM Cloud Session with API key
2021/09/30 19:37:37 [INFO] Configured Region: us-south
2021/09/30 19:37:41 Configuring SoftLayer Session with API key
2021/09/30 19:37:41 Configuring IBM Cloud Session with API key
2021/09/30 19:37:41 [INFO] Configured Region: us-south
2021/09/30 19:37:49 Configuring SoftLayer Session with API key
2021/09/30 19:37:49 Configuring IBM Cloud Session with API key
2021/09/30 19:37:49 [INFO] Configured Region: us-south
2021/09/30 19:37:53 Configuring SoftLayer Session with API key
2021/09/30 19:37:53 Configuring IBM Cloud Session with API key
2021/09/30 19:37:53 [INFO] Configured Region: us-south
2021/09/30 19:37:58 Configuring SoftLayer Session with API key
2021/09/30 19:37:58 Configuring IBM Cloud Session with API key
2021/09/30 19:37:58 [INFO] Configured Region: us-south
2021/09/30 19:38:01 Configuring SoftLayer Session with API key
2021/09/30 19:38:01 Configuring IBM Cloud Session with API key
2021/09/30 19:38:01 [INFO] Configured Region: us-south
--- PASS: TestAccIBMIAMAuthorizationPolicyDelegatorRole (30.76s)
PASS
ok  	github.com/IBM-Cloud/terraform-provider-ibm/ibm	34.096s