Add @return tag to Javadoc in the method getPendingTransactions().

Signed-off-by: Ade Lucas <[email protected]>

plugin-api/src/main/java/org/hyperledger/besu/plugin/services/transactionpool/TransactionPoolService.java

@@ -27,6 +27,10 @@ public interface TransactionPoolService extends BesuService {
   /** Disables the transaction pool. */
   void enableTransactionPool();
 
-  /** Get the transaction pool content */
+  /**
+   * Returns the collection of pending transactions.
+   *
+   * @return a collection of pending transactions
+   */
   Collection<? extends PendingTransaction> getPendingTransactions();
 }