[NFC][doc] Mark P1857R3 as partial implemented

Signed-off-by: yronglin <[email protected]>

Author: yronglin

clang/www/cxx_status.html

@@ -926,7 +926,14 @@ <h2 id="cxx20">C++20 implementation status</h2>
       </tr>
       <tr>
         <td><a href="https://wg21.link/p1857r3">P1857R3</a></td>
-        <td class="none" align="center">No</td>
+        <td class="partial" align="center">
+          <details>
+            <summary>>Clang 21(Partial)</summary>
+            The restriction 'A module directive may only appear as
+            the first preprocessing tokens in a file' was supported
+            in clang-21.
+          </details>
+        </td>
       </tr>
       <tr>
         <td><a href="https://wg21.link/p2115r0">P2115R0</a></td>