sdk: Disable new rustc warnings

The issue here seems to be that
the `panic!` and `unreachable!()` macros used in the tests return `!`.
In the future, `!` will not fallback to `()`, which is what `dependency_on_unit_never_type_fallback` checks.
`add_event_handler` expects a function that returns an `EventHandlerResult`, but it is only implemented for `()`, not for `!`.

A solution could be to implement that trait for `!` but it is an unstable feature right now.

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

crates/matrix-sdk/src/event_handler/mod.rs

@@ -692,6 +692,7 @@ mod tests {
     }
 
     #[async_test]
+    #[allow(dependency_on_unit_never_type_fallback)]
     async fn add_room_event_handler() -> crate::Result<()> {
         let client = logged_in_client(None).await;
 
@@ -753,6 +754,7 @@ mod tests {
     }
 
     #[async_test]
+    #[allow(dependency_on_unit_never_type_fallback)]
     async fn remove_event_handler() -> crate::Result<()> {
         let client = logged_in_client(None).await;