Fix LRANGE usage in non-stream redis (#105)

We `LPUSH` onto front of processing queue, so we should
`LRANGE` the end of the queue when looking for messages
to reenqueue.

omniqueue/src/backends/redis/fallback.rs

@@ -244,15 +244,15 @@ async fn reenqueue_timed_out_messages<R: RedisConnection>(
 
     let mut conn = pool.get().await?;
 
-    let keys: Vec<RawPayload> = conn.lrange(processing_queue_key, 0, 1).await?;
+    let keys: Vec<RawPayload> = conn.lrange(processing_queue_key, -1, -1).await?;
 
     // If the key is older than now, it means we should be processing keys
     let validity_limit = KsuidMs::new(Some(OffsetDateTime::now_utc() - ack_deadline), None)
         .to_string()
         .into_bytes();
 
     if !keys.is_empty() && keys[0] <= validity_limit {
-        let keys: Vec<RawPayload> = conn.lrange(processing_queue_key, 0, BATCH_SIZE).await?;
+        let keys: Vec<RawPayload> = conn.lrange(processing_queue_key, -BATCH_SIZE, -1).await?;
         for key in keys {
             if key <= validity_limit {
                 let internal = internal_from_list(&key)?;