test: Drop OpenCensus based metric exporter initialisation

The knativetest.Flags.EmitMetrics flag is no longer supported after
the migration to OpenTelemetry. This commit removes the conditional
initialisation to align with the new metrics system.

Author: khrm

test/util.go

@@ -146,10 +146,6 @@ func initializeLogsAndMetrics(t *testing.T) {
 		flag.Parse()
 		flag.Set("alsologtostderr", "true")
 		logging.InitializeLogger()
-
-		// if knativetest.Flags.EmitMetrics {
-		logging.InitializeMetricExporter(t.Name())
-		//}
 	})
 }