init covergroup: print, fix

calc_tb.sv

@@ -81,7 +81,7 @@ initial begin
 
     wait (valid);
 
-    $$display("Coverage: %.2f,  %.2f", cg::get_coverage(), cover_inst.get_coverage());
+    $display("Coverage: %.2f,  %.2f", cg::get_coverage(), cover_inst.get_coverage());
 
     $stop;