address review comments

opentelemetry/proto/metrics/v1/metrics.proto

@@ -29,6 +29,25 @@ option go_package = "go.opentelemetry.io/proto/otlp/metrics/v1";
 // storage, OR can be embedded by other protocols that transfer OTLP metrics
 // data but do not implement the OTLP protocol.
 //
+// MetricsData
+// ├── ResourceMetrics
+// │ ├── Resource
+// │ ├── SchemaURL
+// │ └── ScopeMetrics
+// │    ├── Scope
+// │    ├── SchemaURL
+// │    └── Metric
+// │       ├── Name
+// │       ├── Description
+// │       ├── Unit
+// │       └── data
+// │          ├── Gauge
+// │          ├── Sum
+// │          ├── Histogram
+// │          ├── ExponentialHistogram
+// │          └── Summary
+// └── ...
+//
 // The main difference between this message and collector protocol is that
 // in this message there will not be any "control" or "metadata" specific to
 // OTLP protocol.
@@ -97,25 +116,6 @@ message ScopeMetrics {
 // - DataPoint contains timestamps, attributes, and one of the possible value type
 //   fields.
 //
-// MetricsData
-// ├── ResourceMetrics
-// │ ├── Resource
-// │ ├── SchemaURL
-// │ └── ScopeMetrics
-// │    ├── Scope
-// │    ├── SchemaURL
-// │    └── Metric
-// │       ├── Name
-// │       ├── Description
-// │       ├── Unit
-// │       └── data
-// │          ├── Gauge
-// │          ├── Sum
-// │          ├── Histogram
-// │          ├── ExponentialHistogram
-// │          └── Summary
-// └── ...
-//
 //    Data [One of Gauge, Sum, Histogram, Summary, ...]
 //  +-----------+
 //  |...        |  // Metadata about the Data.