chore: update account id variable usage

Author: PriyeshM1

examples/basic/main.tf

@@ -82,9 +82,7 @@ module "cost_anomaly_detection" {
     }
   }
   tags = var.tags
-  accounts_id_to_name = {
-    "1234567890" = "mgmt"
-  }
+  accounts_id_to_name_parameter_arn = "arn:aws:ssm:eu-west-2:0123456778:parameter/myorg/configmaps/accounts_id_to_name_mapping"
   identity_center_start_url = null
   identity_center_role      = null
 }

examples/existing_sns/main.tf

@@ -64,9 +64,7 @@ module "cost_anomaly_detection" {
     }
   }
 
-  accounts_id_to_name = {
-    "1234567890" = "mgmt"
-  }
+  accounts_id_to_name_parameter_arn = "arn:aws:ssm:eu-west-2:0123456778:parameter/myorg/configmaps/accounts_id_to_name_mapping"
   identity_center_start_url = null
   identity_center_role      = null
 }

variables.tf

@@ -69,7 +69,7 @@ variable "tags" {
 
 variable "accounts_id_to_name_parameter_arn" {
   description = "The ARN of your parameter containing the your account ID to name mapping. This ARN will be attached to lambda execution role as a resource, therefore a valid resource must exist. e.g 'arn:aws:ssm:eu-west-2:0123456778:parameter/myorg/configmaps/accounts_id_to_name_mapping' to enable the lambda retrieve values from ssm."
-  type        = map(string)
+  type        = string
   default     = null
 }