Enable approval-voting-parallel by default on kusama (#6218)

The approval-voting-parallel introduced with
https://github.com/paritytech/polkadot-sdk/pull/4849 has been tested on
`versi` and approximately 3 weeks on parity's existing kusama nodes
https://github.com/paritytech/devops/issues/3583, things worked as
expected, so enable it by default on all kusama nodes in the next
release.

The next step will be enabling by default on polkadot if no issue
arrises while running on kusama.

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Signed-off-by: Alexandru Gheorghe <[email protected]>