Bump core from baac24a to 4c34e78 (#518)

Bumps [core](https://github.com/microsoft/typespec) from `baac24a` to
`4c34e78`.
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/microsoft/typespec/commit/4c34e787477d3ab3b75ad14a6d03911341a07305"><code>4c34e78</code></a>
Fix visibility conflict with base models (<a
href="https://redirect.github.com/microsoft/typespec/issues/3049">#3049</a>)</li>
<li><a
href="https://github.com/microsoft/typespec/commit/095c7dd8d481518028f5f39692491ff255e9640b"><code>095c7dd</code></a>
OpenAPI3: Fix multipart union part conflict (<a
href="https://redirect.github.com/microsoft/typespec/issues/3050">#3050</a>)</li>
<li>See full diff in <a
href="https://github.com/microsoft/typespec/compare/baac24ac0061910339304ae629fd9317a4e1f03e...4c34e787477d3ab3b75ad14a6d03911341a07305">compare
view</a></li>
</ul>
</details>
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