substreams tier1 http://localhost:9000/healthz returns text/plain instead of application/json

[matthewdarwin]

tier1 http://localhost:9000/healthz returns text/plain instead of application/json.

tier2 properly returns application/json.

(port 9000 being wherever substreams-tier1-grpc-listen-addr is listening.)

[matthewdarwin]

Closing in favour of: https://github.com/streamingfast/firehose-core/issues/8