Upgrade the Prometheus client to v1.11.1. This commit is the result of running: ``` go get github.com/prometheus/client_golang@v1.11.1 \ && go mod tidy && go mod vendor ``` See https://github.com/prometheus/client_golang/security/advisories/GHSA-cg3q-j54f-5p7p **What this PR does / why we need it**: Upgrades `github.com/prometheus/client_golang` to v1.11.1, where the vulnerability has been fixed.