Revert "test(GitHub CI): disable TestNG HTML logs"

This reverts commit f2325c6.

It didn't seem to make any difference - other than different (unhelpful)
runtime output. Seeing the change removes all listeners, maybe I needed
to add a basic listener back in.

autotest/OldTests/build.sbt

@@ -24,8 +24,6 @@ enablePlugins(TestNGPlugin)
 testNGOutputDirectory := (target.value / "testng").absolutePath
 
 testNGParameters ++= Seq("-log", autotestBuildConfig.value.getInt("tests.verbose").toString)
-// Disable generating the HTML report, as it's running out of memory on GitHub Actions.
-testNGParameters ++= Seq("-usedefaultlisteners", "false")
 
 testNGSuites := {
   val tc = autotestBuildConfig.value.getConfig("tests")