Increase number of concurrent batches to better handle the long tail …

…of slow downloads

crates/subspace-farmer/src/farmer_cache.rs

@@ -654,7 +654,7 @@ where
         downloading_pieces_stream
             // This allows to schedule new batch while previous batches partially completed, but
             // avoids excessive memory usage like when all futures are created upfront
-            .buffer_unordered(SYNC_CONCURRENT_BATCHES * 2)
+            .buffer_unordered(SYNC_CONCURRENT_BATCHES * 10)
             // Simply drain everything
             .for_each(|()| async {})
             .await;