Silicon Valley’s moves to get rid of President Trump from social media represent a display of power the companies have avoided making for almost four years. Now Twitter Inc., Facebook Inc. and others must work out what comes next.Is a span of a couple of days, Twitter and Facebook-Mr. Trump’s main social-media megaphones-took action to put an end to the president’s personal accounts or online communities devoted to him, citing rules suppressing content that fuels violence. They were joined by companies such as Snap Inc. and Reddit Inc.Apple Inc., Amazon.com Inc. and Alphabet Inc’s Google also made steps to boot Parler, a social-media app and website that has increased in popularity among conservatives-and which some rioters had used to encourage Wednesday’s attack at the US Capitol, according to screenshots viewed by The Wall Street Journal.