message: Add comment to streamingprf_test's limitFromHash().
diff: @@ -24,6 +24,7 @@ import (
  commonpb "github.com/google/tink/go/proto/common_go_proto"
  )
  +// limitFromHash returns the maximum output bytes from a HKDF using hash.
  func limitFromHash(t *testing.T, hash commonpb.HashType) (limit int) {
  t.Helper()
  switch hash {
  