Do not force collators to update after enabling async backing (#1920)

The validators are checking if async backing is enabled by checking the
version of the runtime api. If the runtime api is upgraded by a runtime
upgrade, the validators start to also enable the async backing logic.
However, just because async backing is enabled, it doesn't mean that all
collators and parachain runtimes have upgraded. This pull request fixes
an issue about advertising collations to the relay chain when it has
async backing enabled, but the collator is still using the old
networking protocol. The implementation is actually backwards compatible
as we can not expect that everyone directly upgrades. However, the
collation advertisement logic was requiring V2 networking messages after
async backing was enabled, which was wrong. This is now fixed by this
pull request.

Closes: https://github.com/paritytech/polkadot-sdk/issues/1923



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Co-authored-by: eskimor <[email protected]>