WASHINGTON — The Supreme Court on Thursday sided with Google, Twitter and Facebook in lawsuits seeking to hold them liable for terrorist attacks. But the justices sidestepped the big issue hovering over the cases, the federal law that shields social media companies from being sued over content posted by others.The justices unanimously rejected a lawsuit alleging that the companies allowed their platforms to be used to aid and abet an attack at a Turkish nightclub that killed 39 people in 2017.In the case of an …