ffi: remove is_encrypted field from RoomInfo

It turns out this will cause a network request if the encryption info hasn't been loaded before, which is the case for opening a client in offline mode. It will slow down displaying the room list or loading the room info in general.

bindings/matrix-sdk-ffi/src/room_info.rs

@@ -23,7 +23,6 @@ pub struct RoomInfo {
     is_space: bool,
     is_tombstoned: bool,
     is_favourite: bool,
-    is_encrypted: bool,
     canonical_alias: Option<String>,
     alternative_aliases: Vec<String>,
     membership: Membership,
@@ -77,7 +76,6 @@ impl RoomInfo {
             is_space: room.is_space(),
             is_tombstoned: room.is_tombstoned(),
             is_favourite: room.is_favourite(),
-            is_encrypted: room.is_encrypted().await.unwrap_or(false),
             canonical_alias: room.canonical_alias().map(Into::into),
             alternative_aliases: room.alt_aliases().into_iter().map(Into::into).collect(),
             membership: room.state().into(),