Bump smallvec from 1.13.2 to 1.14.0 in /src/rust/engine (#21976)

Bumps [smallvec](https://github.com/servo/rust-smallvec) from 1.13.2 to
1.14.0.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/servo/rust-smallvec/releases">smallvec's
releases</a>.</em></p>
<blockquote>
<h2>v1.14.0</h2>
<h2>What's Changed</h2>
<ul>
<li>Implement <code>MallocSizeOf</code> for SmallVec (v1) by <a
href="https://github.com/nicoburns"><code>@​nicoburns</code></a> in <a
href="https://redirect.github.com/servo/rust-smallvec/pull/370">servo/rust-smallvec#370</a></li>
</ul>
<h2>New Contributors</h2>
<ul>
<li><a href="https://github.com/nicoburns"><code>@​nicoburns</code></a>
made their first contribution in <a
href="https://redirect.github.com/servo/rust-smallvec/pull/370">servo/rust-smallvec#370</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/servo/rust-smallvec/compare/v1.13.2...v1.14.0">https://github.com/servo/rust-smallvec/compare/v1.13.2...v1.14.0</a></p>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/servo/rust-smallvec/commit/174f4f02566d7377aa0e8f9566e73f21f14ce4eb"><code>174f4f0</code></a>
Version 1.14.0</li>
<li><a
href="https://github.com/servo/rust-smallvec/commit/eaeb87182da3d35574e26dbccc12d58a127063d3"><code>eaeb871</code></a>
Bump locked hongfuzz version</li>
<li><a
href="https://github.com/servo/rust-smallvec/commit/cd9f7d3c9a6ea74e4aef713f720c8c0e37330479"><code>cd9f7d3</code></a>
Implement MallocSizeOf for SmallVec (v1)</li>
<li><a
href="https://github.com/servo/rust-smallvec/commit/03d90694561cb4843727b1beef025283667efebb"><code>03d9069</code></a>
Make test_size test aware of target pointer width and &quot;union&quot;
feature.</li>
<li>See full diff in <a
href="https://github.com/servo/rust-smallvec/compare/v1.13.2...v1.14.0">compare
view</a></li>
</ul>
</details>
<br />


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Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Benjy Weinberger <[email protected]>