Bump core from 91f0042 to 48099f0 (#1591)

Bumps [core](https://github.com/microsoft/typespec) from `91f0042` to
`48099f0`.
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/microsoft/typespec/commit/48099f0109c7ec4c21f16eac3b19ce23a3973fca"><code>48099f0</code></a>
Support replacing ctors (<a
href="https://redirect.github.com/microsoft/typespec/issues/4487">#4487</a>)</li>
<li><a
href="https://github.com/microsoft/typespec/commit/063d7ede1dc70a09240df551f0bcede9f110a0d3"><code>063d7ed</code></a>
Add Mutator API to experimental sub export (<a
href="https://redirect.github.com/microsoft/typespec/issues/4290">#4290</a>)</li>
<li>See full diff in <a
href="https://github.com/microsoft/typespec/compare/91f0042a57fff1dc071c6325ff5258271413ab35...48099f0109c7ec4c21f16eac3b19ce23a3973fca">compare
view</a></li>
</ul>
</details>
<br />


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