Bump dokka-gradle-plugin from 1.6.20 to 1.6.21 (#3678)

Summary:
Bumps [dokka-gradle-plugin](https://github.com/Kotlin/dokka) from 1.6.20 to 1.6.21.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a href="https://github.com/Kotlin/dokka/releases">dokka-gradle-plugin's releases</a>.</em></p>
<blockquote>
<h2>1.6.21 Beta</h2>
<p>This is a bugfix release that mostly enables building documentation for multiplatform projects that utilize <code>.klib</code> libraries.</p>
<h2>Changes</h2>
<ul>
<li>Support Kotlin 1.6.21</li>
<li>Update <code>jsoup</code> dependency to avoid <a href="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-37714">CVE-2021-37714</a> (<a href="https://github-redirect.dependabot.com/Kotlin/dokka/issues/2448">https://github.com/facebook/flipper/issues/2448</a>)</li>
</ul>
<h2>Bugfixes</h2>
<ul>
<li>Support <code>KLIB</code> libraries for common platform, previously led to <code>ERROR CLASS</code> instead of references in documentation (<a href="https://github-redirect.dependabot.com/Kotlin/dokka/issues/2441">https://github.com/facebook/flipper/issues/2441</a>)</li>
<li>Fixed a maven plugin build problem related to coroutines which only occurred in multi-module builds (<a href="https://github-redirect.dependabot.com/Kotlin/dokka/issues/2461">https://github.com/facebook/flipper/issues/2461</a>)</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="b69a7d431f"><code>b69a7d4</code></a> Update documentation and examples to Dokka 1.6.21 (<a href="https://github-redirect.dependabot.com/Kotlin/dokka/issues/2465">https://github.com/facebook/flipper/issues/2465</a>)</li>
<li><a href="981ca7fc61"><code>981ca7f</code></a> Set <code>finalizeCoroutines</code> to false for maven runner (<a href="https://github-redirect.dependabot.com/Kotlin/dokka/issues/2461">https://github.com/facebook/flipper/issues/2461</a>)</li>
<li><a href="a7d7e07f23"><code>a7d7e07</code></a> Update Dokka version to 1.6.21</li>
<li><a href="a8c1a64285"><code>a8c1a64</code></a> Update Kotlin to 1.6.21 (<a href="https://github-redirect.dependabot.com/Kotlin/dokka/issues/2454">https://github.com/facebook/flipper/issues/2454</a>)</li>
<li><a href="68eaffc19a"><code>68eaffc</code></a> Update Jsoup to 1.14.3 (<a href="https://github-redirect.dependabot.com/Kotlin/dokka/issues/2448">https://github.com/facebook/flipper/issues/2448</a>)</li>
<li><a href="e0cc2adacc"><code>e0cc2ad</code></a> Support KLIB for Common platform (<a href="https://github-redirect.dependabot.com/Kotlin/dokka/issues/2441">https://github.com/facebook/flipper/issues/2441</a>)</li>
<li><a href="d868eaba22"><code>d868eab</code></a> Use common gradle+kotlin versions across gradle integration tests (<a href="https://github-redirect.dependabot.com/Kotlin/dokka/issues/2287">https://github.com/facebook/flipper/issues/2287</a>)</li>
<li>See full diff in <a href="https://github.com/Kotlin/dokka/compare/v1.6.20...v1.6.21">compare view</a></li>
</ul>
</details>
<br />

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</details>

Pull Request resolved: https://github.com/facebook/flipper/pull/3678

Reviewed By: lblasa

Differential Revision: D36127807

Pulled By: passy

fbshipit-source-id: a4230dcafba57aa30de8a7a65ee74485ae53ec73

build.gradle

@@ -14,7 +14,7 @@ buildscript {
         classpath 'com.android.tools.build:gradle:7.0.4'
         classpath 'com.vanniktech:gradle-maven-publish-plugin:0.19.0'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$KOTLIN_VERSION"
-        classpath "org.jetbrains.dokka:dokka-gradle-plugin:1.6.20"
+        classpath "org.jetbrains.dokka:dokka-gradle-plugin:1.6.21"
     }
 }