[deps]: Update dtolnay/rust-toolchain digest to 4cda84d (#1540)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
|
[dtolnay/rust-toolchain](https://redirect.github.com/dtolnay/rust-toolchain)
([changelog](https://redirect.github.com/dtolnay/rust-toolchain/compare/29eef336d9b2848a0b548edc03f92a220660cdb8..4cda84d5c5c54efe2404f9d843567869ab1699d4))
| action | digest | `29eef33` → `4cda84d` |

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