CommCompGraph: handle three lines in legend

plot/comm_comp.py

@@ -659,6 +659,7 @@ class CommCompGraph:
         shrink_plot_legend = {  # dict to tell how much to shrink the plot according to the number of legend rows:
             1: 0.8,
             2: 0.8,
+            3: 0.8,
             4: 0.72,
             5: 0.65
         }