chore(obs): drop 44 dead_code blankets from the metrics tree (#6086)

crates/obs/src/metrics/schema/node_disk.rs

@@ -12,8 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#![allow(dead_code)]
-
 use crate::{MetricDescriptor, MetricName, MetricSubsystem, new_gauge_md};
 use std::sync::LazyLock;