Follow-up to make #7124 target iPhone 11 (#7555)

* Avoid using features newer than iPhone 11 in client_impl_base.cpp

* Adding a note in the changelog

CHANGELOG.md

@@ -9,6 +9,7 @@
 * Fixed diverging history due to a bug in the replication code when setting default null values (embedded objects included) ([#7536](https://github.com/realm/realm-core/issues/7536)).
 * Version 19.39.33523 of MSVC would crash when compiling for arm64 in release mode ([PR #7533](https://github.com/realm/realm-core/pull/7533)).
 * Null pointer exception may be triggered when logging out and async commits callbacks not executed ([#7434](https://github.com/realm/realm-core/issues/7434), since v13.26.0)
+* Fixed building for iPhone simulators targeting deployment target 11 ([#7554](https://github.com/realm/realm-core/pull/7554)).
 
 ### Breaking changes
 * Updated default base URL to be `https://services.cloud.mongodb.com` to support the new domains (was `https://realm.mongodb.com`). ([PR #7534](https://github.com/realm/realm-core/pull/7534))

src/realm/sync/noinst/client_impl_base.cpp

@@ -2365,10 +2365,10 @@ Status Session::receive_download_message(const DownloadMessage& message)
         return Status::OK();
 
     bool is_flx = m_conn.is_flx_sync_connection();
-    int64_t query_version = is_flx ? message.query_version.value() : 0;
+    int64_t query_version = is_flx ? *message.query_version : 0;
 
     // If this is a PBS connection, then every download message is its own complete batch.
-    bool last_in_batch = is_flx ? message.last_in_batch.value() : true;
+    bool last_in_batch = is_flx ? *message.last_in_batch : true;
     auto batch_state = last_in_batch ? sync::DownloadBatchState::LastInBatch : sync::DownloadBatchState::MoreToCome;
     if (is_steady_state_download_message(batch_state, query_version))
         batch_state = DownloadBatchState::SteadyState;