Update changelog for mu-server 2.2.8 release

[Copilot]

A new mu-server release (2.2.8) was available, but the docs changelog still listed 2.2.7 as the latest entry. This updates the changelog to reflect the current release and its primary dependency bump.

• Changelog currency

  • Added a new top release block in src/main/resources/views/changelog.html for 2.2.8.

• Release note content

  • Recorded the upstream change shipped in this release: Netty upgrade to 4.1.133.

<div class="release minor">
    <h2>2.2.8</h2>
    <ul>
        <li>Upgraded Netty to 4.1.133</li>
    </ul>
</div>