return joined member count of room for pushrules instead of hardcoded 10

im not sure what the TODO is trying to say here,
but since it's many years old and conduwuit is
fast, i dont see an issue with this.

Signed-off-by: strawberry <strawberry@puppygock.gay>

src/service/pusher/mod.rs

@@ -200,7 +200,13 @@ impl Service {
 
         let ctx = PushConditionRoomCtx {
             room_id: room_id.to_owned(),
-            member_count: 10_u32.into(), // TODO: get member count efficiently
+            member_count: UInt::from(
+                services()
+                    .rooms
+                    .state_cache
+                    .room_joined_count(room_id)?
+                    .unwrap_or(1) as u32,
+            ),
             user_id: user.to_owned(),
             user_display_name: services()
                 .users