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/xhost_test.go

@@ -11,7 +11,7 @@ import (
 func TestXHostOp(t *testing.T) {
 	t.Parallel()
 
-	checkOpBehaviour(t, []opBehaviourTestCase{
+	checkOpBehaviour(t, 0, []opBehaviourTestCase{
 		{"xcbChangeHosts revert", 0xbeef, hst.EX11, xhostOp("chronos"), []stub.Call{
 			call("verbosef", stub.ExpectArgs{"inserting entry %s to X11", []any{xhostOp("chronos")}}, nil, nil),
 			call("xcbChangeHosts", stub.ExpectArgs{xcb.HostMode(xcb.HostModeInsert), xcb.Family(xcb.FamilyServerInterpreted), "localuser\x00chronos"}, nil, stub.UniqueError(1)),