superfluous response.WriteHeader call from client_golang

[mrfelton]

Getting this error from lndmon repeatedly in our logs:

2021/03/26 09:06:14 http: superfluous response.WriteHeader call from github.com/prometheus/client_golang/prometheus/promhttp.(*responseWriterDelegator).WriteHeader (delegator.go:58)

Posts like these suggest it would be fixed by updating to a recent version of client_golang

https://github.com/prometheus/statsd_exporter/issues/257 https://github.com/prometheus/client_golang/issues/730 https://github.com/google/cadvisor/issues/2537 https://github.com/thanos-io/thanos/issues/1086