Greendale is losing another one of its favorite alum. According to TV Guide, Yvette Nicole Brown—who plays one of our favorite characters on TV, Shirley—will not appear in the upcoming season of Community so that she can spend time with her father, who is sick. She told the magazine, “It was a difficult decision for me to make, but I had to choose my dad.” With the departure of Donald Glover and now Brown, the show is in the process of casting two new characters for sixth season …