chore: deduplicate auth policy in example (#475)

Author: shemau

examples/complete/main.tf

@@ -102,7 +102,7 @@ module "mongodb" {
   use_ibm_owned_encryption_key = false
   use_same_kms_key_for_backups = false
   kms_key_crn                  = module.key_protect_all_inclusive.keys["icd.${local.data_key_name}"].crn
-  backup_encryption_key_crn    = module.key_protect_all_inclusive.keys["icd.${local.data_key_name}"].crn
+  backup_encryption_key_crn    = module.key_protect_all_inclusive.keys["icd.${local.backups_key_name}"].crn
   service_credential_names = {
     "mongodb_admin" : "Administrator",
     "mongodb_operator" : "Operator",