Remove unnecessary DataChannelKey default constructor

Explicitly writing a default constructor is not necessary here,
because there are no other constructors in the class that could
suppress automatic compiler generation of it, and all the struct
members are also default-constructible.

Signed-off-by: Razvan Cojocaru <[email protected]>

Author: rzvncj

openvpn/ssl/proto.hpp

@@ -1702,9 +1702,6 @@ class ProtoContext : public logging::LoggingMixin<OPENVPN_DEBUG_PROTO,
         // for example if cipher/digest are pushed.
         struct DataChannelKey
         {
-            //! Default do-nothing constructor.
-            DataChannelKey() = default;
-
             OpenVPNStaticKey key;
             std::optional<CryptoDCInstance::RekeyType> rekey_type;
         };