Fix /jumptodate using wrong MSC feature flag (#7563)

As reported by @turt2live, https://matrix.to/#/!EMAlzkQQlZGEVTkDnD:matrix.org/$gnoVWQnIkYYL1i1cL8A4qRKJCFpNtq0Oj5khpzOq1mQ?via=half-shot.uk&via=matrix.org&via=element.io

Also fixes camelCase typo

src/SlashCommands.tsx

@@ -334,7 +334,7 @@ export const Commands = [
                     );
                     dis.dispatch({
                         action: Action.ViewRoom,
-                        eventId,
+                        event_id: eventId,
                         highlighted: true,
                         room_id: roomId,
                     });