U.S. stock index futures slipped on Friday, even as Wall Street’s main indexes looked to finish the year with handsome gains for the third time in a row, supported by massive stimulus, and strong retail participation. Futures tracking the S&P 500 and the Dow slipped 0.2 percent on the last day of 2021, a day after scaling intraday all-time highs. Tesla Inc. slipped half a percent in premarket trading as it recalled more than 475,000 of its Model 3 and Model S electric cars to address rearview camera and trunk issues that increase the risk of crashing. The S&P 500 and Dow hit all-time highs this week, as optimism from early data suggesting the Omicron variant was less virulent than other strains outweighed worries from record-high surge in U.S. cases and warnings of disruptions ahead. Aiding sentiment was a string of upbeat data this week, including a report that showed …