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