enable unreachable_pub lint

This causes some other lints to start firing too (which is good), but
I'm going to fix them in follow-up commits to keep things organized.

src/api/client_server/search.rs

@@ -14,7 +14,7 @@ use std::collections::BTreeMap;
 /// Searches rooms for messages.
 ///
 /// - Only works if the user is currently joined to the room (TODO: Respect history visibility)
-pub async fn search_events_route(
+pub(crate) async fn search_events_route(
     body: Ruma<search_events::v3::Request>,
 ) -> Result<search_events::v3::Response> {
     let sender_user = body.sender_user.as_ref().expect("user is authenticated");