BEIJING—China’s economy grew slightly slower than expected in the second quarter, weighed down by higher raw materials costs and new COVID-19 outbreaks. Expectations build that policymakers may have to do more to support the recovery. Gross domestic product (GDP) expanded 7.9 percent in the April-June quarter from a year earlier, official data showed on July 15, missing expectations of an 8.1 percent rise in a Reuters poll of economists. Growth slowed significantly from a record 18.3 percent expansion in the January-March period, when the year-on-year growth rate was heavily skewed by the COVID-induced slump in the first quarter of 2020. Retail sales and industrial output growth was slower in June, the latter dragged by a sharp fall in motor vehicle production, while NBS data also showed a cooling in China’s housing market, a key engine of growth. But June activity data still beat expectations, providing some relief to investors concerned …