Update ListVolumesByMetricName description for Metric Name Pricing (#1681)

Co-authored-by: ci.datadog-api-spec <packages@datadoghq.com>

Author: api-clients-generation-pipeline[bot]

.generator/schemas/v2/openapi.yaml

@@ -137855,9 +137855,9 @@ paths:
   /api/v2/metrics/{metric_name}/volumes:
     get:
       description: |-
-        View hourly average metric volumes for the given metric name over the look back period.
-
-        Custom metrics generated in-app from other products will return `null` for ingested volumes.
+        View hourly average cardinality for the given metric name over the look back period.
+        For Metric Name Pricing customers, view total point volume for the given metric name
+        over the look back period.
       operationId: ListVolumesByMetricName
       parameters:
         - $ref: "#/components/parameters/MetricName"

src/datadogV2/api/api_metrics.rs

@@ -2037,9 +2037,9 @@ impl MetricsAPI {
         }
     }
 
-    /// View hourly average metric volumes for the given metric name over the look back period.
-    ///
-    /// Custom metrics generated in-app from other products will return `null` for ingested volumes.
+    /// View hourly average cardinality for the given metric name over the look back period.
+    /// For Metric Name Pricing customers, view total point volume for the given metric name
+    /// over the look back period.
     pub async fn list_volumes_by_metric_name(
         &self,
         metric_name: String,
@@ -2065,9 +2065,9 @@ impl MetricsAPI {
         }
     }
 
-    /// View hourly average metric volumes for the given metric name over the look back period.
-    ///
-    /// Custom metrics generated in-app from other products will return `null` for ingested volumes.
+    /// View hourly average cardinality for the given metric name over the look back period.
+    /// For Metric Name Pricing customers, view total point volume for the given metric name
+    /// over the look back period.
     pub async fn list_volumes_by_metric_name_with_http_info(
         &self,
         metric_name: String,