The R&B singers will meet in the latest installment of ‘Verzuz’ — R&B’s strongest power is its ability to help us heal. Voices leap from speakers and headphones to soothe our pain. In the 1980s, women turned to Phyllis Hyman and Karyn White to let go of their superwoman capes. In the ’90s, Toni Braxton and Mary J. Blige figured out how…