#draft proto2 fails to push into grafana cloud

[dzmitry-lahoda]

• used https://github.com/prometheus/client_model/blob/master/io/prometheus/client/metrics.proto
• either with current repo master or rebuilt of proto2 get this

---- test::push stdout ----
thread 'test::push' panicked at 'called `Result::unwrap()` on an `Err` value: Msg("unexpected status code 400 Bad Request while pushing to https://prometheus-prod-10-prod-us-central-0.grafana.net/api/prom/push with body `proto: WriteRequest: wiretype end group for non-group\n`")', prometheus-sink/src/lib.rs:37:10
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

on grafana cloud