[clang] Document p1703 not needed

We list p1703 as unimplemented, but it is subsumed by p1857.

Reviewed By: tbaeder

Differential Revision: https://reviews.llvm.org/D123120

clang/www/cxx_status.html

@@ -1176,10 +1176,11 @@ code. This issue is expected to be rectified soon.
       </tr>
       <tr>
         <td><a href="https://wg21.link/p1811r0">P1811R0</a></td>
-        <td rowspan="2" class="none" align="center">No</td>
+        <td class="none" align="center">No</td>
       </tr>
       <tr>
         <td><a href="https://wg21.link/p1703r1">P1703R1</a></td>
+        <td class="none" align="center">Subsumed by P1857</td>
       </tr>
       <tr> <!-- from Belfast -->
         <td><a href="https://wg21.link/p1874r1">P1874R1</a></td>