Shares of technology heavyweights dragged the S&P 500 lower Friday and toward a weekly loss, snapping a three-week winning streak. The week has been marked by big swings among shares of individual companies and a rotation between some of the market’s recent winners and losers. The information technology sector—one of the market’s biggest winners this year—was the biggest laggard of the S&P 500’s 11 sectors for the week. The...