[clang] [NFC][clang] Mark P3868R1 as implemented (PR #197181)

[Yanzuo Liu via cfe-commits]

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@@ -336,7 +336,7 @@ <h2 id="cxx26">C++2c implementation status</h2>
  <tr>
    <td>Allow <tt>#line</tt> before module declarations</td>
    <td><a href="https://wg21.link/P3868R1">P3868R1</a></td>
-   <td class="none" align="center">No</td>
+   <td class="full" align="center">Clang 23</td>
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zwuis wrote:

```suggestion
   <td class="full" align="center">Clang 21</td>
```

https://github.com/llvm/llvm-project/pull/197181