bump futures for broken upstream dep in tokio (pin-utils).

[zippy]

PR summary

update futures crate because of dependency issues.

testing/benchmarking notes

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followups

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- summary of change [PR#1234](https://github.com/holochain/holochain-rust/pull/1234)

documentation

• this code has been documented according to our docs checklist