Update envelope.proto

Co-authored-by: Mark Lodato <[email protected]>

Author: AdamZWu

envelope.proto

@@ -9,7 +9,7 @@ message Envelope {
   oneof payload_encoding {
     // Raw bytes. In JSON, this is encoded as base64.
     bytes payload = 1;
-    // Unicode string, where the signed byte stream is the UTF-8 encoding. In JSON, this is a regular unicode string.
+    // Unicode string, where the signed byte stream (SERIALIZED_BODY) is the UTF-8 encoding of `payloadUtf8`. In JSON, this is a regular string.
     string payloadUtf8 = 4;
   }