use event content in account_data service api instead of full events

This eliminates the possibility of passing an event that has a
mismatching type, reducing the space of possible invalid states.

src/api/client_server/sync/msc3575.rs

@@ -25,7 +25,8 @@ use tracing::{debug, error};
 
 use super::{load_timeline, share_encrypted_room};
 use crate::{
-    service::rooms::timeline::PduCount, services, Ar, Error, Ra, Result,
+    service::{account_data, rooms::timeline::PduCount},
+    services, Ar, Error, Ra, Result,
 };
 
 #[allow(clippy::too_many_lines)]
@@ -645,7 +646,13 @@ pub(crate) async fn sync_events_v4_route(
                     services()
                         .account_data
                         .global_changes_since(&sender_user, globalsince)?
-                        .into_values()
+                        .into_iter()
+                        .map(|(event_type, content)| {
+                            account_data::raw_global_event_from_parts(
+                                &event_type,
+                                &content,
+                            )
+                        })
                         .collect()
                 } else {
                     Vec::new()