Bump syn from 2.0.52 to 2.0.53 (#2347)

Bumps [syn](https://github.com/dtolnay/syn) from 2.0.52 to 2.0.53.
<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>2.0.53</h2>
<ul>
<li>Implement Copy, Clone, and ToTokens for syn::parse::Nothing (<a
href="https://redirect.github.com/dtolnay/syn/issues/1597">#1597</a>)</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/dtolnay/syn/commit/32dcf8df303c7181d95325f159ffbb1870a73e70"><code>32dcf8d</code></a>
Release 2.0.53</li>
<li><a
href="https://github.com/dtolnay/syn/commit/fd1f2aa9979c557e5b95c85f35b8949b8059153f"><code>fd1f2aa</code></a>
Merge pull request <a
href="https://redirect.github.com/dtolnay/syn/issues/1597">#1597</a>
from dtolnay/copyprintnothing</li>
<li><a
href="https://github.com/dtolnay/syn/commit/4f6c0528d63874495ce23d197a898cd63cb04d60"><code>4f6c052</code></a>
Implement ToTokens for syn::parse::Nothing</li>
<li><a
href="https://github.com/dtolnay/syn/commit/3f37543794e5d43952399847a2ecbc1eb39f609f"><code>3f37543</code></a>
Implement Copy for syn::parse::Nothing</li>
<li><a
href="https://github.com/dtolnay/syn/commit/36a412217d5217fab5657ab03ebcf29102d87a64"><code>36a4122</code></a>
Update test suite to nightly-2024-03-16</li>
<li><a
href="https://github.com/dtolnay/syn/commit/bd931069f5adb81168e7e6186ead0663cc605257"><code>bd93106</code></a>
Revert &quot;Temporarily disable nightly testing due to libLLVM link
issue&quot;</li>
<li><a
href="https://github.com/dtolnay/syn/commit/06166a77b7d465b0e4c45e1a2162f15031d7f722"><code>06166a7</code></a>
Update test suite to nightly-2024-03-09</li>
<li><a
href="https://github.com/dtolnay/syn/commit/ed545e75d8fdcab5078789ad25fc0efadc14e59b"><code>ed545e7</code></a>
Work around doc_markdown lint in test_precedence</li>
<li><a
href="https://github.com/dtolnay/syn/commit/7aef1edbba28afe1bb6f9ddc0b5095dcd5135849"><code>7aef1ed</code></a>
Temporarily disable nightly testing due to libLLVM link issue</li>
<li><a
href="https://github.com/dtolnay/syn/commit/556b10bf201264172e4b840f8cf1be38b8d75738"><code>556b10b</code></a>
Update test suite to nightly-2024-03-06</li>
<li>Additional commits viewable in <a
href="https://github.com/dtolnay/syn/compare/2.0.52...2.0.53">compare
view</a></li>
</ul>
</details>
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