refactor: replace collect().is_empty() with next().is_none() in tests (#18902)

Co-authored-by: Alexey Shekhirin <5773434+shekhirin@users.noreply.github.com>

crates/chain-state/src/in_memory.rs

@@ -1380,8 +1380,7 @@ mod tests {
     #[test]
     fn test_canonical_in_memory_state_canonical_chain_empty() {
         let state: CanonicalInMemoryState = CanonicalInMemoryState::empty();
-        let chain: Vec<_> = state.canonical_chain().collect();
-        assert!(chain.is_empty());
+        assert!(state.canonical_chain().next().is_none());
     }
 
     #[test]

crates/transaction-pool/src/pool/pending.rs

@@ -921,8 +921,7 @@ mod tests {
         assert!(removed.is_empty());
 
         // Verify that retrieving transactions from an empty pool yields nothing
-        let all_txs: Vec<_> = pool.all().collect();
-        assert!(all_txs.is_empty());
+        assert!(pool.all().next().is_none());
     }
 
     #[test]