docs(byoc): allow RDS service-linked role creation in AWS BYOC policy (cube-js#11114)

The AWS BYOC IAM policy grants iam:CreateServiceLinkedRole only for the EKS
service names. Customers enabling the AI Engineer external RDS feature in a
fresh account (one that has never created an RDS instance, so AWSServiceRoleForRDS
does not yet exist) hit:

  RDS CreateDBInstance -> InvalidParameterValue: Unable to create the resource.
  Verify that you have permission to create service linked role.

Add rds.amazonaws.com to the iam:AWSServiceName allowlist so the role can create
the RDS service-linked role on first use.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: bsod90

docs-mintlify/admin/deployment/dedicated/aws/byoc.mdx

@@ -199,7 +199,8 @@ actual account ID.
                     "iam:AWSServiceName": [
                         "eks.amazonaws.com",
                         "eks-nodegroup.amazonaws.com",
-                        "eks-fargate.amazonaws.com"
+                        "eks-fargate.amazonaws.com",
+                        "rds.amazonaws.com"
                     ]
                 }
             }