Bumps [actions/checkout](https://github.com/actions/checkout) from 2.4.0 to 3.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a href="https://github.com/actions/checkout/releases">actions/checkout's releases</a>.</em></p>
<blockquote>
<h2>v3.0.0</h2>
<ul>
<li>Update default runtime to node16</li>
</ul>
</blockquote>
</details>
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a href="https://github.com/actions/checkout/blob/main/CHANGELOG.md">actions/checkout's changelog</a>.</em></p>
<blockquote>
<h1>Changelog</h1>
<h2>v2.3.1</h2>
<ul>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/284">Fix default branch resolution for .wiki and when using SSH</a></li>
</ul>
<h2>v2.3.0</h2>
<ul>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/278">Fallback to the default branch</a></li>
</ul>
<h2>v2.2.0</h2>
<ul>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/258">Fetch all history for all tags and branches when fetch-depth=0</a></li>
</ul>
<h2>v2.1.1</h2>
<ul>
<li>Changes to support GHES (<a href="https://github-redirect.dependabot.com/actions/checkout/pull/236">here</a> and <a href="https://github-redirect.dependabot.com/actions/checkout/pull/248">here</a>)</li>
</ul>
<h2>v2.1.0</h2>
<ul>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/191">Group output</a></li>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/199">Changes to support GHES alpha release</a></li>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/184">Persist core.sshCommand for submodules</a></li>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/163">Add support ssh</a></li>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/179">Convert submodule SSH URL to HTTPS, when not using SSH</a></li>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/157">Add submodule support</a></li>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/144">Follow proxy settings</a></li>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/141">Fix ref for pr closed event when a pr is merged</a></li>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/128">Fix issue checking detached when git less than 2.22</a></li>
</ul>
<h2>v2.0.0</h2>
<ul>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/108">Do not pass cred on command line</a></li>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/107">Add input persist-credentials</a></li>
<li><a href="https://github-redirect.dependabot.com/actions/checkout/pull/104">Fallback to REST API to download repo</a></li>
</ul>
<h2>v2 (beta)</h2>
<ul>
<li>Improved fetch performance
<ul>
<li>The default behavior now fetches only the SHA being checked-out</li>
</ul>
</li>
<li>Script authenticated git commands
<ul>
<li>Persists <code>with.token</code> in the local git config</li>
<li>Enables your scripts to run authenticated git commands</li>
<li>Post-job cleanup removes the token</li>
<li>Coming soon: Opt out by setting <code>with.persist-credentials</code> to <code>false</code></li>
</ul>
</li>
<li>Creates a local branch
<ul>
<li>No longer detached HEAD when checking out a branch</li>
<li>A local branch is created with the corresponding upstream branch set</li>
</ul>
</li>
<li>Improved layout</li>
</ul>

</blockquote>
<p>... (truncated)</p>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="a12a3943b4"><code>a12a394</code></a> update readme for v3 (<a href="https://github-redirect.dependabot.com/actions/checkout/issues/708">#708</a>)</li>
<li><a href="8f9e05e482"><code>8f9e05e</code></a> Update to node 16 (<a href="https://github-redirect.dependabot.com/actions/checkout/issues/689">#689</a>)</li>
<li><a href="230611dbd0"><code>230611d</code></a> Change secret name for PAT to not start with GITHUB_ (<a href="https://github-redirect.dependabot.com/actions/checkout/issues/623">#623</a>)</li>
<li>See full diff in <a href="https://github.com/actions/checkout/compare/v2.4.0...v3">compare view</a></li>
</ul>
</details>
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