fix(op-devstack): correct EnableReqRespSync default to false

[DenseDenise]

found this issue from #17496 (CI checks failed)

Fixes test failure by correcting the default value introduced in 3f2bf28 - req-resp sync should be opt-in, not opt-out.

cc @nonsense

[nonsense]

By default the op-node runs with this value equal to true. I don't see a reason why the default in tests should be false, the current version of develop is just fine in my opinion.

[DenseDenise]

By default the op-node runs with this value equal to true. I don't see a reason why the default in tests should be false, the current version of develop is just fine in my opinion.

Or should we try other way to avoiding the CI fails?

[nonsense]

@DenseDenise the test that failed is flaky (TestUnsafeChainStalling_DisabledReqRespSync), it needs the NoDiscovery modifier for the network, and it is not on develop unfortunately. I have fixed it as part of #17751 , but will probably merge sooner so that we have fewer flakes.

Thanks!

[nonsense]

Added a PR for it at #17918