Deprecate gfe2_reloadable_flag_quic_deprecate_draining_streams.

Remove draining_streams from QuicSession.

PiperOrigin-RevId: 314130389
Change-Id: If3ce6b7fba67faf3f044b6bcea7d63d42c7bf087
diff --git a/quic/core/quic_stream.h b/quic/core/quic_stream.h
index fe9d04c..930fd17 100644
--- a/quic/core/quic_stream.h
+++ b/quic/core/quic_stream.h
@@ -539,8 +539,7 @@
   // If initialized, reset this stream at this deadline.
   QuicTime deadline_;
 
-  // True if this stream has entered draining state. Only used when
-  // quic_deprecate_draining_streams is true.
+  // True if this stream has entered draining state.
   bool was_draining_;
 
   // Indicates whether this stream is bidirectional, read unidirectional or