Update dependency prometheus_client to v0.8.0
Update dependency prometheus_client to v0.8.0

trungdtbk/faucet,anarkiwi/faucet,REANNZ/faucet,mwutzke/faucet,trungdtbk/faucet,shivarammysore/faucet,anarkiwi/faucet,shivarammysore/faucet,mwutzke/faucet,faucetsdn/faucet,REANNZ/faucet,faucetsdn/faucet