Bump thiserror from 1.0.37 to 1.0.38 in /cmd/pinniped-proxy (#5818)

Bumps [thiserror](https://github.com/dtolnay/thiserror) from 1.0.37 to
1.0.38.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/dtolnay/thiserror/releases">thiserror's
releases</a>.</em></p>
<blockquote>
<h2>1.0.38</h2>
<ul>
<li>Documentation improvements</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/dtolnay/thiserror/commit/74bfe75eb25ba9d39b0ae5b570d611855cbc5086"><code>74bfe75</code></a>
Release 1.0.38</li>
<li><a
href="https://github.com/dtolnay/thiserror/commit/cfc7d8c959da82ba405043aae7e56c91aecf1b50"><code>cfc7d8c</code></a>
Update build status badge</li>
<li><a
href="https://github.com/dtolnay/thiserror/commit/db78fa2cd88b5dd7fecadad55b17d0100fd43280"><code>db78fa2</code></a>
Update ui test suite to nightly-2022-12-15</li>
<li><a
href="https://github.com/dtolnay/thiserror/commit/c25a71081339aa8b62efc231409e3e6b4e0ce306"><code>c25a710</code></a>
Time out workflows after 45 minutes</li>
<li><a
href="https://github.com/dtolnay/thiserror/commit/464e2e798eea0985af3c2c16cc55866e2918f774"><code>464e2e7</code></a>
Merge pull request <a
href="https://github-redirect.dependabot.com/dtolnay/thiserror/issues/200">#200</a>
from dtolnay/displayattr</li>
<li><a
href="https://github.com/dtolnay/thiserror/commit/4b06a3e2637812a13d501d14a80edafade8dff98"><code>4b06a3e</code></a>
Add test of Display impl nested inside display attribute</li>
<li><a
href="https://github.com/dtolnay/thiserror/commit/29ee95ef47a74c00bdbcf253bae46964a241894c"><code>29ee95e</code></a>
Ui test changes for trybuild 1.0.66</li>
<li>See full diff in <a
href="https://github.com/dtolnay/thiserror/compare/1.0.37...1.0.38">compare
view</a></li>
</ul>
</details>
<br />


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