Fix a warning in the QUIC build

Previously:

./base/internal/logging.h:351:32: warning: comparison of integers of different signs: 'const int' and 'const unsigned long' [-Wsign-compare]
DEFINE_CHECK_OP_IMPL(Check_GE, >=)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
./base/internal/logging.h:338:30: note: expanded from macro 'DEFINE_CHECK_OP_IMPL'
    if (ABSL_PREDICT_TRUE(v1 op v2))                                \
                          ~~ ^  ~~
./third_party/absl/base/optimization.h:182:51: note: expanded from macro 'ABSL_PREDICT_TRUE'
#define ABSL_PREDICT_TRUE(x) (__builtin_expect(!!(x), 1))
                                                  ^
third_party/quic/core/quic_session.cc:1260:3: note: in instantiation of function template specialization 'Check_GEImpl<int, unsigned long>' requested here
  DCHECK_GE(dynamic_stream_map_.size() + pending_stream_map_.size(),

gfe-relnote: n/a Warning fix, no functional change.
PiperOrigin-RevId: 239654830
Change-Id: I29f1793a4f328f7aac8ff5372eb156f9fcb9fd1a
diff --git a/quic/core/quic_session.cc b/quic/core/quic_session.cc
index e5eb207..2332070 100644
--- a/quic/core/quic_session.cc
+++ b/quic/core/quic_session.cc
@@ -1257,7 +1257,8 @@
 }
 
 size_t QuicSession::GetNumDynamicOutgoingStreams() const {
-  DCHECK_GE(dynamic_stream_map_.size() + pending_stream_map_.size(),
+  DCHECK_GE(static_cast<size_t>(dynamic_stream_map_.size() +
+                                pending_stream_map_.size()),
             num_dynamic_incoming_streams_);
   return dynamic_stream_map_.size() + pending_stream_map_.size() -
          num_dynamic_incoming_streams_;