prompb: Add note about experimental state of native histograms
@@ -75,6 +75,7 @@ message Histogram {
repeated Bucket bucket = 3; // Ordered in increasing order of upper_bound, +Inf bucket is optional.
// Everything below here is for native histograms (also known as sparse histograms).
+ // Native histograms are an experimental feature without stability guarantees.
// schema defines the bucket schema. Currently, valid numbers are -4 <= n <= 8.
// They are all for base-2 bucket schemas, where 1 is a bucket boundary in each case, and
