Amazon Studios/Magnolia Pictures opened mid-’90s-set comedy Landline with Jenny Slate, Edie Falco, Abby Quinn, Jay Duplass and John Turturro in four theaters Friday, easily capturing the best per-theater average among the specialties opening this frame and the second-best overall at just over $13,000. The 2017 Sundance title was a stand-out in an otherwise fairly slow weekend for limited-release films trying to carve a niche as counter-programming to summer blockbusters…