Update Rust crate smallvec to v1.15.0 (#28469)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [smallvec](https://redirect.github.com/servo/rust-smallvec) |
workspace.dependencies | minor | `1.14.0` -> `1.15.0` |

---

### Release Notes

<details>
<summary>servo/rust-smallvec (smallvec)</summary>

###
[`v1.15.0`](https://redirect.github.com/servo/rust-smallvec/releases/tag/v1.15.0)

[Compare
Source](https://redirect.github.com/servo/rust-smallvec/compare/v1.14.0...v1.15.0)

#### What's Changed

- Fix typos by
[@&#8203;waywardmonkeys](https://redirect.github.com/waywardmonkeys) in
[https://github.com/servo/rust-smallvec/pull/373](https://redirect.github.com/servo/rust-smallvec/pull/373)
- Implement bincode2 encode/decode support for smallvec v1 by
[@&#8203;markbt](https://redirect.github.com/markbt) in
[https://github.com/servo/rust-smallvec/pull/375](https://redirect.github.com/servo/rust-smallvec/pull/375)

#### New Contributors

- [@&#8203;markbt](https://redirect.github.com/markbt) made their first
contribution in
[https://github.com/servo/rust-smallvec/pull/375](https://redirect.github.com/servo/rust-smallvec/pull/375)

**Full Changelog**:
https://github.com/servo/rust-smallvec/compare/v1.14.0...v1.15.0

</details>

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---

Release Notes:

- N/A

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Cargo.lock

@@ -13236,9 +13236,9 @@ dependencies = [
 
 [[package]]
 name = "smallvec"
-version = "1.14.0"
+version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7fcf8323ef1faaee30a44a340193b1ac6814fd9b7b4e88e9d4519a3e4abe1cfd"
+checksum = "8917285742e9f3e1683f0a9c4e6b57960b7314d0b08d30d1ecd426713ee2eee9"
 dependencies = [
  "serde",
 ]