Update module github.com/prometheus/client_golang to v1.21.0#750

openshift-merge-bot[bot] merged 1 commit intorelease-1.8netobserv/network-observability-console-plugin:release-1.8from

konflux/mintmaker/release-1.8/github.com-prometheus-client_golang-1.xnetobserv/network-observability-console-plugin:konflux/mintmaker/release-1.8/github.com-prometheus-client_golang-1.xCopy head branch name to clipboard