docs: Missing monitoring metric `go_memstats_gc_cpu_fraction`

[philipaconrad]

Short description

Since Go 1.18, it seems that Prometheus has removed the go_memstats_gc_cpu_fraction, which is reported on the Monitoring docs page as a STABLE metric.

If someone goes looking for that metric in Prometheus / Grafana charts while setting up an OPA deployment, they definitely won't see it! :sweat_smile:

Expected solution

The docs should reflect the removal of the metric, either with an explicit deprecation/removal note, or by just removing the table row for go_memstats_gc_cpu_fraction.

Additional context

• https://github.com/prometheus/client_golang/issues/1500