testing/protocmp: surface comment about unused Transform options

Change-Id: I83bdb0f3f937f745b5758c282e1bd58203a8c784
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/237221
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/testing/protocmp/xform.go b/testing/protocmp/xform.go
index 4372532..25d1302 100644
--- a/testing/protocmp/xform.go
+++ b/testing/protocmp/xform.go
@@ -157,10 +157,10 @@
 // This does not directly transform higher-order composite Go types.
 // For example, []*foopb.Message is not transformed into []Message,
 // but rather the individual message elements of the slice are transformed.
+//
+// Note that there are currently no custom options for Transform,
+// but the use of an unexported type keeps the future open.
 func Transform(...option) cmp.Option {
-	// NOTE: There are currently no custom options for Transform,
-	// but the use of an unexported type keeps the future open.
-
 	// addrType returns a pointer to t if t isn't a pointer or interface.
 	addrType := func(t reflect.Type) reflect.Type {
 		if k := t.Kind(); k == reflect.Interface || k == reflect.Ptr {