Working the grind in Miami, a pair of old friends from high school get back in touch and decide to form a rap group in “Rap Sh!t,” created by “Insecure” star Issa Rae, who remains off camera this time around. Music stardom might actually be in Shawna and Mia’s grasp, if they can get enough traction, push through their insecurities and get a handle on their evolving friendship, as well their complicated personal lives. Shawna (Aida Osman, who is also a writer on the show) works the front desk at a hotel and her instincts are on the brainy side, leaning in the direction of conscious rap: “I want…
