Increase QuicConnectionArena size to 1280.

This is the amount of memory it uses when compiled to use libstdc++ in debug mode (which is the default mode things are compiled on Linux).

PiperOrigin-RevId: 449367692

quiche/quic/core/quic_one_block_arena.h

diff --git a/quiche/quic/core/quic_one_block_arena.h b/quiche/quic/core/quic_one_block_arena.h
index a988a55..cb44217 100644
--- a/quiche/quic/core/quic_one_block_arena.h
+++ b/quiche/quic/core/quic_one_block_arena.h
@@ -70,7 +70,7 @@
 
 // QuicConnections currently use around 1KB of polymorphic types which would
 // ordinarily be on the heap. Instead, store them inline in an arena.
-using QuicConnectionArena = QuicOneBlockArena<1248>;
+using QuicConnectionArena = QuicOneBlockArena<1280>;
 
 }  // namespace quic