internal/system: optional op check parallelism

The PipeWire Op check cannot be made parallel due to the OS interaction.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/system/dbus_test.go

@@ -18,7 +18,7 @@ import (
 func TestDBusProxyOp(t *testing.T) {
 	t.Parallel()
 
-	checkOpBehaviour(t, []opBehaviourTestCase{
+	checkOpBehaviour(t, 0, []opBehaviourTestCase{
 		{"dbusProxyStart", 0xdead, 0xff, &dbusProxyOp{
 			final:  dbusNewFinalSample(4),
 			out:    new(linePrefixWriter), // panics on write