Remove kv_cmd_total_* from the metrics metadata

It's recently been flagged that we generate Prometheus documentation for some metrics which are not actually exposed to Prometheus. This means our Metrics Documentation is incorrect.

The kv_cmd_total_* metrics for example do not exist in Prometheus, but are documented as if they are. There might be others. We'd need to go over every metric and make sure this is tagged correctly as "prometheus": false.