Auto merge of #28833 - servo:dependabot/cargo/rustc-demangle-0.1.21, r=jdm

Bump rustc-demangle from 0.1.18 to 0.1.21

Bumps [rustc-demangle](https://github.com/alexcrichton/rustc-demangle) from 0.1.18 to 0.1.21.
<details>
<summary>Commits</summary>
<ul>
<li><a href="2811a1ad6f"><code>2811a1a</code></a> Bump to 0.1.21</li>
<li><a href="670f024fba"><code>670f024</code></a> Merge pull request <a href="https://github-redirect.dependabot.com/alexcrichton/rustc-demangle/issues/55">#55</a> from eddyb/const-values</li>
<li><a href="fd906f850f"><code>fd906f8</code></a> v0: demangle ADT const values.</li>
<li><a href="232789841b"><code>2327898</code></a> v0: demangle array and tuple const values.</li>
<li><a href="245357ab2e"><code>245357a</code></a> v0: demangle <code>&amp;</code> and <code>&amp;mut</code> const values.</li>
<li><a href="3cf31b9a08"><code>3cf31b9</code></a> v0: demangle <code>str</code> const values using string literals.</li>
<li><a href="ef262636d9"><code>ef26263</code></a> Merge pull request <a href="https://github-redirect.dependabot.com/alexcrichton/rustc-demangle/issues/56">#56</a> from eddyb/const-value-prereqs</li>
<li><a href="6b3c45971b"><code>6b3c459</code></a> v0: don't use <code>fmt::Debug</code> for printing const <code>char</code>s.</li>
<li><a href="a20a29a55f"><code>a20a29a</code></a> v0: add test showing a const <code>char</code> double-quote not being escaped.</li>
<li><a href="e31ad72108"><code>e31ad72</code></a> v0: make <code>print_const</code> more self-contained, like <code>print_type</code>.</li>
<li>Additional commits viewable in <a href="https://github.com/alexcrichton/rustc-demangle/compare/0.1.18...0.1.21">compare view</a></li>
</ul>
</details>
<br />

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Cargo.lock

@@ -5246,9 +5246,9 @@ dependencies = [
 
 [[package]]
 name = "rustc-demangle"
-version = "0.1.18"
+version = "0.1.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6e3bad0ee36814ca07d7968269dd4b7ec89ec2da10c4bb613928d3077083c232"
+checksum = "7ef03e0a2b150c7a90d01faf6254c9c48a41e95fb2a8c2ac1c6f0d2b9aefc342"
 
 [[package]]
 name = "rustc-hash"