Fix iOS compilation of transport parameters

gfe-relnote: n/a, trivial build-only change
PiperOrigin-RevId: 244095858
Change-Id: I2dc56cfe56efe26f58f4eba0df0c7be0bc26f5d4

quic/core/crypto/transport_parameters.h

diff --git a/quic/core/crypto/transport_parameters.h b/quic/core/crypto/transport_parameters.h
index 251d141..c52b3c8 100644
--- a/quic/core/crypto/transport_parameters.h
+++ b/quic/core/crypto/transport_parameters.h
@@ -52,7 +52,7 @@
         const IntegerParameter& param);
 
    private:
-    friend class TransportParameters;
+    friend struct TransportParameters;
     // Constructors for initial setup used by TransportParameters only.
     // This constructor sets |default_value| and |min_value| to 0, and
     // |max_value| to kVarInt62MaxValue.