Remove requested_server_name_ field from StreamInfo (#19102)

Since the requested_server_name_ was moved to ConnectionInfoProvider, this field is useless now.

Risk Level: low
Testing: n/a
Docs Changes: n/a
Release Notes: n/a
Platform Specific Features: no

Signed-off-by: He Jie Xu <hejie.xu@intel.com>

source/common/stream_info/stream_info_impl.h

@@ -468,7 +468,6 @@ struct StreamInfoImpl : public StreamInfo {
   uint64_t bytes_sent_{};
   Network::Address::InstanceConstSharedPtr legacy_upstream_local_address_;
   const Network::ConnectionInfoProviderSharedPtr downstream_connection_info_provider_;
-  std::string requested_server_name_;
   const Http::RequestHeaderMap* request_headers_{};
   Http::RequestIdStreamInfoProviderSharedPtr request_id_provider_;
   absl::optional<DownstreamTiming> downstream_timing_;