gfe-relnote: n/a, fix some compiler errors in QUICHE.

Reported in:
https://github.com/envoyproxy/envoy/issues/10422 of -Wsign-compare under GCC.
https://github.com/envoyproxy/envoy/issues/10767 of missing copy assignment under clang10.

PiperOrigin-RevId: 309489267
Change-Id: I69cb5ed3a6b1bd447da44bb241c3d81bf73865ab
diff --git a/quic/core/quic_framer.cc b/quic/core/quic_framer.cc
index 7bf49ab..30a3742 100644
--- a/quic/core/quic_framer.cc
+++ b/quic/core/quic_framer.cc
@@ -5415,7 +5415,7 @@
     const uint64_t ack_range = iter->Length() - 1;
 
     if (writer->remaining() < ecn_size ||
-        writer->remaining() - ecn_size <
+        static_cast<size_t>(writer->remaining() - ecn_size) <
             QuicDataWriter::GetVarInt62Len(gap) +
                 QuicDataWriter::GetVarInt62Len(ack_range)) {
       // ACK range does not fit, truncate it.