gfe-relnote: change logs about window update frames from DLOG(INFO) to DVLOG(1).

When using MESSAGE frames in WebRTC, we never send any retransmittable packets.
QUIC sends a window update frame every few packets to provide a retransmittable
frame, from here:
http://google3/third_party/quic/core/quic_session.cc?l=1468&rcl=264213918

That results in log spam from received window updates on the other endpoint.

PiperOrigin-RevId: 264681195
Change-Id: Ib4d62b4acb1b6dfb9d9e96994df2b4712f3b33e2

quic/core/quic_session.cc

diff --git a/quic/core/quic_session.cc b/quic/core/quic_session.cc
index a335804..15fcf24 100644
--- a/quic/core/quic_session.cc
+++ b/quic/core/quic_session.cc
@@ -474,10 +474,10 @@
       QuicUtils::GetInvalidStreamId(connection_->transport_version())) {
     // This is a window update that applies to the connection, rather than an
     // individual stream.
-    QUIC_DLOG(INFO) << ENDPOINT
-                    << "Received connection level flow control window "
-                       "update with byte offset: "
-                    << frame.byte_offset;
+    QUIC_DVLOG(1) << ENDPOINT
+                  << "Received connection level flow control window "
+                     "update with byte offset: "
+                  << frame.byte_offset;
     flow_controller_.UpdateSendWindowOffset(frame.byte_offset);
     return;
   }