Rename quic::kMaxPacketSize to quic::kMaxOutgoingPacketSize

As part of cl/242197597, QUIC now has separate values for maximum incoming and outgoing packet sizes. This CL renames the constant to be clearer.

gfe-relnote: constant rename, no functional impact
PiperOrigin-RevId: 242708648
Change-Id: I3f440ba44b9c12394026116aaecdd2c166cc63b6
diff --git a/quic/core/quic_framer.cc b/quic/core/quic_framer.cc
index 4fd6936..c24a23c 100644
--- a/quic/core/quic_framer.cc
+++ b/quic/core/quic_framer.cc
@@ -880,7 +880,7 @@
       free_bytes >= GetMinAckFrameSize(version_.transport_version,
                                        PACKET_6BYTE_PACKET_NUMBER);
   if (can_truncate) {
-    // Truncate the frame so the packet will not exceed kMaxPacketSize.
+    // Truncate the frame so the packet will not exceed kMaxOutgoingPacketSize.
     // Note that we may not use every byte of the writer in this case.
     QUIC_DLOG(INFO) << ENDPOINT
                     << "Truncating large frame, free bytes: " << free_bytes;