Bump checker-qual from 3.20.0 to 3.21.0

Bumps [checker-qual](https://github.com/typetools/checker-framework) from 3.20.0 to 3.21.0.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a href="https://github.com/typetools/checker-framework/releases">checker-qual's releases</a>.</em></p>
<blockquote>
<h2>Checker Framework 3.21.0</h2>
<h2>Version 3.21.0 (December 17, 2021)</h2>
<p><strong>User-visible changes:</strong></p>
<p>The Checker Framework now more precisely computes the type of a switch expression.</p>
<p><strong>Implementation details:</strong></p>
<p>The dataflow framework now analyzes switch expressions and switch statements that use the new <code>-&gt;</code> case syntax. To do so, a new node, SwitchExpressionNode, was added.</p>
<p><strong>Closed issues:</strong>
<a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/2373">#2373</a>, <a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4934">#4934</a>, <a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4977">#4977</a>, <a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4979">#4979</a>, <a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4987">#4987</a>.</p>
</blockquote>
</details>
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a href="https://github.com/typetools/checker-framework/blob/master/docs/CHANGELOG.md">checker-qual's changelog</a>.</em></p>
<blockquote>
<h2>Version 3.21.0 (December 17, 2021)</h2>
<p><strong>User-visible changes:</strong></p>
<p>The Checker Framework now more precisely computes the type of a switch expression.</p>
<p><strong>Implementation details:</strong></p>
<p>The dataflow framework now analyzes switch expressions and switch statements
that use the new <code>-&gt;</code> case syntax. To do so, a new node, SwitchExpressionNode,
was added.</p>
<p><strong>Closed issues:</strong>
<a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/2373">#2373</a>, <a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4934">#4934</a>, <a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4977">#4977</a>, <a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4979">#4979</a>, <a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4987">#4987</a>.</p>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://github.com/typetools/checker-framework/commit/2e12f3b68436f03d1e0c39c0f29a05231bae0db1"><code>2e12f3b</code></a> new release 3.21.0</li>
<li><a href="https://github.com/typetools/checker-framework/commit/87599736c90984ada01c064c5185d420be1484c8"><code>8759973</code></a> Prep for release.</li>
<li><a href="https://github.com/typetools/checker-framework/commit/cd9a2a37017a34671beca2d5c60130f7b1a43171"><code>cd9a2a3</code></a> JointJavacJavaParserVisitor now handles switch expressions  (<a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4992">#4992</a>)</li>
<li><a href="https://github.com/typetools/checker-framework/commit/689b03302db5812c9245cc0cd93f9b4b28dad5d3"><code>689b033</code></a> CheckerMain: don't crash on nonexistent directories (<a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4991">#4991</a>)</li>
<li><a href="https://github.com/typetools/checker-framework/commit/35f31b76705a842402ec389e44f3cd7c9258bb6e"><code>35f31b7</code></a> Dataflow: fall through never happens in switch rules. (<a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4984">#4984</a>)</li>
<li><a href="https://github.com/typetools/checker-framework/commit/946fc030888be9d81dcd2fc3e01e741edeb36890"><code>946fc03</code></a> add note to documentation of Owning about why it is a declaration annotation,...</li>
<li><a href="https://github.com/typetools/checker-framework/commit/dd9dde7074a755cf29ec7838e78109e403f09dfd"><code>dd9dde7</code></a> Remove SKIP-REQUIRE-JAVADOC</li>
<li><a href="https://github.com/typetools/checker-framework/commit/0967219fb7d20914c7e5a30b27d57dbdbaacc12a"><code>0967219</code></a> Add support for switch expressions in dataflow (<a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4982">#4982</a>)</li>
<li><a href="https://github.com/typetools/checker-framework/commit/4a5a7d98e138c9e76d3f4cebf397fcfa7d84af52"><code>4a5a7d9</code></a> Use property for errorprone version number. (<a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4990">#4990</a>)</li>
<li><a href="https://github.com/typetools/checker-framework/commit/4bd99aa3ffc9409cead933328d1485f19966db91"><code>4bd99aa</code></a> Fix multiple case constants. (<a href="https://github-redirect.dependabot.com/typetools/checker-framework/issues/4985">#4985</a>)</li>
<li>Additional commits viewable in <a href="https://github.com/typetools/checker-framework/compare/checker-framework-3.20.0...checker-framework-3.21.0">compare view</a></li>
</ul>
</details>
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Fixes #932

COPYBARA_INTEGRATE_REVIEW=#932 from google:dependabot/maven/org.checkerframework-checker-qual-3.21.0 fb74a17
PiperOrigin-RevId: 417396970

pom.xml

@@ -79,7 +79,7 @@
       <dependency>
         <groupId>org.checkerframework</groupId>
         <artifactId>checker-qual</artifactId>
-        <version>3.20.0</version>
+        <version>3.21.0</version>
       </dependency>
       <dependency>
         <groupId>junit</groupId>