Use ParsedQuicVersion in QuicMultiplexingStatsCollection

gfe-relnote: refactor, no behavior change, not flag protected
PiperOrigin-RevId: 290150673
Change-Id: Ie60904456122927957bd4a252e71cb623be22b92

quic/core/quic_session.h

diff --git a/quic/core/quic_session.h b/quic/core/quic_session.h
index 0a79842..1e5208a 100644
--- a/quic/core/quic_session.h
+++ b/quic/core/quic_session.h
@@ -463,6 +463,8 @@
     return connection_->transport_version();
   }
 
+  inline ParsedQuicVersion version() const { return connection_->version(); }
+
   bool use_http2_priority_write_scheduler() const {
     return use_http2_priority_write_scheduler_;
   }