Update sort_spec.lua

Author: icemberg

.spec/sorting/sort_spec.lua

@@ -76,5 +76,6 @@ describe("Bogosort", function()
 	check_sort(require("sorting.bogosort"), 5)
 end)
 describe("Countingsort", function()
-	check_sort(require("sorting.countingsort"), nil, true)
+    local countingsort = require("sorting.countingsort")
+    check_sort(countingsort, nil, true)
 end)