Fix warning during terraform plan - 'roles' key is deprecated.
Fix warning during terraform plan - 'roles' key is deprecated.

While running 'make plan' the following warning is shown:
"module.jenkins.aws_iam_instance_profile.jenkins: "roles": [DEPRECATED] Use `role` instead. Only a single role can be passed to an IAM Instance Profile"

This change to 'role' instead of 'roles' and passing a single value instead of a list makes the warning go away.

alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws