Fix histogram dapa point comment about supported boundaries

Fixes: open-telemetry#259

Signed-off-by: Bogdan Drutu <bogdandrutu@gmail.com>

opentelemetry/proto/metrics/v1/metrics.proto

@@ -432,6 +432,12 @@ message IntHistogramDataPoint {
   // buckets if a histogram is provided.
   sfixed64 sum = 5;
 
+  // A histogram may optionally contain the distribution of the values in the
+  // population. In that case one the "explicit_bounds" and "bucket_counts"
+  // fields must be defined. Otherwise both fields must be omitted in which case
+  // the distribution of values in the histogram is unknown and only the total
+  // count and sum are known.
+
   // bucket_counts is an optional field contains the count values of histogram
   // for each bucket.
   //
@@ -441,14 +447,6 @@ message IntHistogramDataPoint {
   // the number of elements in explicit_bounds array.
   repeated fixed64 bucket_counts = 6;
 
-  // A histogram may optionally contain the distribution of the values in the population.
-  // In that case one of the option fields below and "buckets" field both must be defined.
-  // Otherwise all option fields and "buckets" field must be omitted in which case the
-  // distribution of values in the histogram is unknown and only the total count and sum are known.
-
-  // explicit_bounds is the only supported bucket option currently.
-  // TODO: Add more bucket options.
-
   // explicit_bounds specifies buckets with explicitly defined bounds for values.
   //
   // This defines size(explicit_bounds) + 1 (= N) buckets. The boundaries for
@@ -508,6 +506,12 @@ message HistogramDataPoint {
   // buckets if a histogram is provided.
   double sum = 5;
 
+  // A histogram may optionally contain the distribution of the values in the
+  // population. In that case one the "explicit_bounds" and "bucket_counts"
+  // fields must be defined. Otherwise both fields must be omitted in which case
+  // the distribution of values in the histogram is unknown and only the total
+  // count and sum are known.
+
   // bucket_counts is an optional field contains the count values of histogram
   // for each bucket.
   //
@@ -517,14 +521,6 @@ message HistogramDataPoint {
   // the number of elements in explicit_bounds array.
   repeated fixed64 bucket_counts = 6;
 
-  // A histogram may optionally contain the distribution of the values in the population.
-  // In that case one of the option fields below and "buckets" field both must be defined.
-  // Otherwise all option fields and "buckets" field must be omitted in which case the
-  // distribution of values in the histogram is unknown and only the total count and sum are known.
-
-  // explicit_bounds is the only supported bucket option currently.
-  // TODO: Add more bucket options.
-
   // explicit_bounds specifies buckets with explicitly defined bounds for values.
   //
   // This defines size(explicit_bounds) + 1 (= N) buckets. The boundaries for