Bump site-shared from e466136 to 777996f (#10605)

Bumps [site-shared](https://github.com/dart-lang/site-shared) from
`e466136` to `777996f`.
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/dart-lang/site-shared/commit/777996f8f9ee179f666c59318d62e09c21251122"><code>777996f</code></a>
Update CI and lints for Dart 3.4 release (<a
href="https://redirect.github.com/dart-lang/site-shared/issues/221">#221</a>)</li>
<li>See full diff in <a
href="https://github.com/dart-lang/site-shared/compare/e466136cd77d715352a7f86a7abf563a1cfce735...777996f8f9ee179f666c59318d62e09c21251122">compare
view</a></li>
</ul>
</details>
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