events: Fix non-link URL
@@ -28,7 +28,7 @@ use crate::{
/// directly will fail.
///
/// This event may also include an `invite_room_state` key inside the event's unsigned data, but
-/// Ruma doesn't currently expose this; see https://github.com/ruma/ruma/issues/998.
+/// Ruma doesn't currently expose this; see [#998](https://github.com/ruma/ruma/issues/998).
///
/// The user for which a membership applies is represented by the `state_key`. Under some
/// conditions, the `sender` and `state_key` may not match - this may be interpreted as the
