Fix coverage threshold ignored for Total line in Summary (#11571)

An incorrect variable is being passed to the `display/2` function on line 353 for the Total line in the coverage summary report. The result is that that Total line will always display in red no matter what the threshold is set to.

Author: sh41

lib/mix/lib/mix/tasks/test.coverage.ex

@@ -350,7 +350,7 @@ defmodule Mix.Tasks.Test.Coverage do
     Mix.shell().info("-----------|--------------------------")
     results |> Enum.sort() |> Enum.each(&display(&1, threshold))
     Mix.shell().info("-----------|--------------------------")
-    display({totals, "Total"}, opts)
+    display({totals, "Total"}, threshold)
     Mix.shell().info("")
   end