ci(deps): update swatinem/rust-cache action to v2.6.0 (#370)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [Swatinem/rust-cache](https://togithub.com/Swatinem/rust-cache) |
action | minor | `v2.5.1` -> `v2.6.0` |

---

### Release Notes

<details>
<summary>Swatinem/rust-cache (Swatinem/rust-cache)</summary>

###
[`v2.6.0`](https://togithub.com/Swatinem/rust-cache/releases/tag/v2.6.0)

[Compare
Source](https://togithub.com/Swatinem/rust-cache/compare/v2.5.1...v2.6.0)

##### What's Changed

- Add "buildjet" as a second `cache-provider` backend
[@&#8203;joroshiba](https://togithub.com/joroshiba) in
[https://github.com/Swatinem/rust-cache/pull/154](https://togithub.com/Swatinem/rust-cache/pull/154)
-   Clean up sparse registry index.
-   Do not clean up src of `-sys` crates.
-   Remove `.cargo/credentials.toml` before saving.

##### New Contributors

- [@&#8203;joroshiba](https://togithub.com/joroshiba) made their first
contribution in
[https://github.com/Swatinem/rust-cache/pull/154](https://togithub.com/Swatinem/rust-cache/pull/154)

**Full Changelog**:
Swatinem/rust-cache@v2.5.1...v2.6.0

</details>

---

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---

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.github/workflows/build.yml

@@ -58,7 +58,7 @@ jobs:
         with:
           toolchain: stable
           target: ${{ matrix.target }}
-      - uses: Swatinem/rust-cache@dd05243424bd5c0e585e4b55eb2d7615cdd32f1f # v2.5.1
+      - uses: Swatinem/rust-cache@b8a6852b4f997182bdea832df3f9e153038b5191 # v2.6.0
         with:
           key: ${{ matrix.target }}
       - name: Install cross