Ensure there is no policy with invalid principal format for AWS Elastic File System (EFS) policy

Invalid principal format. The Principal element contents are not valid.

In AWS Console -

1. Sign in to the AWS Console and go to the Amazon EFS console.
2. Select File Systems.
3. Click the file system that you want to configure. Select Permissions.
4. In the File system policy, select the policy statement.
5. Click Edit and make the necessary changes.

In Terraform -

1. In the aws_efs_file_system_policy resource, configure the policy field accordingly.

References:
https://docs.aws.amazon.com/efs/latest/ug/auth-and-access-control.html
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/efs_file_system_policy