S3 Bucket Arn is mandatory argument when providing S3 Bucket Name

[fossouo]

When we run the mwaa artefact we get below error message :

│ Error: Missing required argument
│
│ with aws_mwaa_environment.mwaa,
│ on main.tf line 23, in resource "aws_mwaa_environment" "mwaa":
│ 23: source_bucket_arn = local.source_bucket_arn
│
│ The argument "source_bucket_arn" is required, but no definition was found.

I have a PR which resolves this dependency. #36