By Lucia Mutikani WASHINGTON (Reuters) - The U.S. economy grew solidly in the second quarter, pulling the level of gross domestic product above its pre-pandemic peak, as massive government aid and vaccinations against COVID-19 fueled spending on goods and travel-related services. The pace of GDP growth reported by the Commerce Department on Thursday was, however, slower than economists had expected. That was because businesses had to again draw down on meager inventories to meet the robust demand. Supply constraints, which have resulted in shortages of motor vehicles and some household applian...