Bump core from 429d74a to 6d6e0c1 (#4491)

Bumps [core](https://github.com/microsoft/typespec) from `429d74a` to
`6d6e0c1`.
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/microsoft/typespec/commit/6d6e0c129ef9e91e8daaaf6f314d31c97fd76f1c"><code>6d6e0c1</code></a>
[python] add mock API tests for Azure.SpecialHeaders.ConditionalRequest
(<a
href="https://redirect.github.com/microsoft/typespec/issues/10783">#10783</a>)</li>
<li><a
href="https://github.com/microsoft/typespec/commit/a4cb9b5be12e6869fbc40028c51a00fbacd4a344"><code>a4cb9b5</code></a>
Bump uuid and <code>@​azure/msal-node</code> in
/packages/http-client-python (<a
href="https://redirect.github.com/microsoft/typespec/issues/10763">#10763</a>)</li>
<li><a
href="https://github.com/microsoft/typespec/commit/1abd5ed38e7d32487e83b65e0b4dfe17c080b8c3"><code>1abd5ed</code></a>
Bump pytest from 8.3.2 to 9.0.3 in
/packages/http-client-python/eng/scripts/c...</li>
<li><a
href="https://github.com/microsoft/typespec/commit/c6d5336d0f9834d07855000820d91b01d322d5a0"><code>c6d5336</code></a>
Bump pytest from 8.3.2 to 9.0.3 in
/packages/http-client-python/tests/require...</li>
<li><a
href="https://github.com/microsoft/typespec/commit/d5cf20e6b9f74c8113590facca13efdaf9b2dab2"><code>d5cf20e</code></a>
build(deps): bump postcss from 8.5.6 to 8.5.12 in
/packages/http-client-pytho...</li>
<li><a
href="https://github.com/microsoft/typespec/commit/6b2b06ebf70a4e7b985b41170401339869283181"><code>6b2b06e</code></a>
build(deps): bump fast-uri from 3.1.0 to 3.1.2 in
/packages/http-client-pytho...</li>
<li><a
href="https://github.com/microsoft/typespec/commit/e4c97dc8588eda3cb7a814ecbf1c23d10c00ed27"><code>e4c97dc</code></a>
build(deps): bump qs from 6.15.0 to 6.15.2 in
/packages/http-client-python (#...</li>
<li><a
href="https://github.com/microsoft/typespec/commit/d72f4f115eb0c2864920a74af1fbc8d4dc7e52dc"><code>d72f4f1</code></a>
[python] update python emitter install with helpful 401 error output (<a
href="https://redirect.github.com/microsoft/typespec/issues/10720">#10720</a>)</li>
<li><a
href="https://github.com/microsoft/typespec/commit/f9d02ed533364e2903d66ac80b72d6c955942fb4"><code>f9d02ed</code></a>
fix: always run npm auth in publish pipeline (<a
href="https://redirect.github.com/microsoft/typespec/issues/10761">#10761</a>)</li>
<li><a
href="https://github.com/microsoft/typespec/commit/2ddbc37be746535e8ec9bdd63e842e1d89d8b9da"><code>2ddbc37</code></a>
Propagate tcgc SerializationOptions for body parameters and responses
(<a
href="https://redirect.github.com/microsoft/typespec/issues/10730">#10730</a>)</li>
<li>Additional commits viewable in <a
href="https://github.com/microsoft/typespec/compare/429d74aaf5e1675c27022a31631e9e0857033f77...6d6e0c129ef9e91e8daaaf6f314d31c97fd76f1c">compare
view</a></li>
</ul>
</details>
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