fix: concat two list of strings then turn it into set

[naihsuanshao]

Summary

To fix this error

Error: Too many function arguments
│ 
│   on .terraform/modules/biohub-s3-readonly/aws-iam-role-s3-readonly/main.tf line 55, in data "aws_iam_policy_document" "s3-bucket-readonly":
│   55:     resources = toset(formatlist("arn:aws:s3:::%s", var.s3_bucket_names), formatlist("arn:aws:s3:::%s/*", var.s3_bucket_names))
│     ├────────────────
│     │ while calling toset(v)
│     │ var.s3_bucket_names is a set of string
│ 
│ Function "toset" expects only 1 argument(s).

Test Plan

Say unittests, or list out steps to verify changes.

References

(Optional) Additional links to provide more context.

[kuannie1]

lgtm! thanks