Update Rust crate tokio to 1.31

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
tokio (source)	dependencies	minor	1.30 -> 1.31

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Release Notes

tokio-rs/tokio (tokio)

v1.31.0: Tokio v1.31.0

Compare Source

Fixed

• io: delegate WriteHalf::poll_write_vectored (#​5914)

Unstable

• rt(unstable): fix memory leak in unstable next-gen scheduler prototype (#​5911)
• rt: expose mean task poll time metric (#​5927)

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