Bump serde from 1.0.154 to 1.0.156 in /cmd/pinniped-proxy (#6082)

Bumps [serde](https://github.com/serde-rs/serde) from 1.0.154 to
1.0.156.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/serde-rs/serde/releases">serde's
releases</a>.</em></p>
<blockquote>
<h2>v1.0.156</h2>
<ul>
<li>Documentation improvements</li>
</ul>
<h2>v1.0.155</h2>
<ul>
<li>Support <code>Serialize</code> and <code>Deserialize</code> impls
for <code>core::ffi::CStr</code> and <code>alloc::ffi::CString</code>
without &quot;std&quot; feature (<a
href="https://redirect.github.com/serde-rs/serde/issues/2374">#2374</a>,
thanks <a
href="https://github.com/safarir"><code>@​safarir</code></a>)</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/serde-rs/serde/commit/54671259aaaf2617b0f27dce6cc519058d4f3a90"><code>5467125</code></a>
Release 1.0.156</li>
<li><a
href="https://github.com/serde-rs/serde/commit/994f7c7924f7fccde5c474644f6d22115586bdee"><code>994f7c7</code></a>
Format with rustfmt 1.5.2-nightly</li>
<li><a
href="https://github.com/serde-rs/serde/commit/7a8e4977e230e2da45bb7e1f75d7a3175b6a7755"><code>7a8e497</code></a>
Merge pull request <a
href="https://redirect.github.com/serde-rs/serde/issues/2401">#2401</a>
from dtolnay/docderive</li>
<li><a
href="https://github.com/serde-rs/serde/commit/fb7b6ea7ea8864a41e78378ca0555ce3f1dd8965"><code>fb7b6ea</code></a>
Enable serde derive feature when built by docs.rs</li>
<li><a
href="https://github.com/serde-rs/serde/commit/063dd5b93f9f0c3181de399132441668fed67029"><code>063dd5b</code></a>
Show derive macros in serde's rustdoc</li>
<li><a
href="https://github.com/serde-rs/serde/commit/a38aa31ade469b034dc8d04c39cc52c0e76c9e75"><code>a38aa31</code></a>
Merge pull request <a
href="https://redirect.github.com/serde-rs/serde/issues/2400">#2400</a>
from Nilstrieb/explicit-reexport</li>
<li><a
href="https://github.com/serde-rs/serde/commit/f42b2581da2bdbb81713a93d3b7e581b81e4332e"><code>f42b258</code></a>
Use explicit re-export of <code>serde_derive</code> to give rustc more
info</li>
<li><a
href="https://github.com/serde-rs/serde/commit/2ba406726f9f84bc3b65ce4e824ae636dfa7dc85"><code>2ba4067</code></a>
Release 1.0.155</li>
<li><a
href="https://github.com/serde-rs/serde/commit/7e9826e17b154b32742b71285349ec042da7ee35"><code>7e9826e</code></a>
Add link to core CStr stabilization announcement</li>
<li><a
href="https://github.com/serde-rs/serde/commit/f4dcc5c918a54712fbf76f50883c6c496d0b8af9"><code>f4dcc5c</code></a>
Merge pull request <a
href="https://redirect.github.com/serde-rs/serde/issues/2374">#2374</a>
from safarir/master</li>
<li>Additional commits viewable in <a
href="https://github.com/serde-rs/serde/compare/v1.0.154...v1.0.156">compare
view</a></li>
</ul>
</details>
<br />


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