chore(deps): Bump syn from 2.0.25 to 2.0.26 (#17994)

Bumps [syn](https://github.com/dtolnay/syn) from 2.0.25 to 2.0.26.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/dtolnay/syn/releases">syn's
releases</a>.</em></p>
<blockquote>
<h2>2.0.26</h2>
<ul>
<li>Implement <code>Spanned</code> for <code>QSelf</code> (<a
href="https://redirect.github.com/dtolnay/syn/issues/1465">#1465</a>)</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/dtolnay/syn/commit/a4d7aa80e32647b1f3e6e8fd80c68aa5125f3c0e"><code>a4d7aa8</code></a>
Release 2.0.26</li>
<li><a
href="https://github.com/dtolnay/syn/commit/ee59842458f2272a874b158f4d222de4a5c20ccc"><code>ee59842</code></a>
Merge pull request <a
href="https://redirect.github.com/dtolnay/syn/issues/1486">#1486</a>
from dtolnay/qselfspan</li>
<li><a
href="https://github.com/dtolnay/syn/commit/9e32a34bbd081b0e453e7515b322047ca48d1e61"><code>9e32a34</code></a>
Implement Spanned for QSelf</li>
<li>See full diff in <a
href="https://github.com/dtolnay/syn/compare/2.0.25...2.0.26">compare
view</a></li>
</ul>
</details>
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