tls_cipher_suites only accept a comma-separated string, as evident in:

https://github.com/hashicorp/nomad/blob/0535dfd414214efd14183bf23d1447f679b57af8/nomad/structs/config/tls.go#L61
https://github.com/hashicorp/nomad/blob/d37ed5c193ac8237666b92bd3f3b0b7e0a8ebfd5/helper/tlsutil/config.go#L405