[clang] Update __cpp_concepts macro (PR #87998)

[Erich Keane via cfe-commits]

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@@ -544,16 +544,8 @@ <h2 id="cxx20">C++20 implementation status</h2>
       </tr>
       <tr> <!-- from Cologne -->
         <td><a href="https://wg21.link/p0848r3">P0848R3</a></td>
-        <td rowspan="1" class="partial" align="center">
-          <details>
-            <summary>Clang 16 (Partial)</summary>
-            Because of other concepts implementation deficits, the __cpp_concepts macro is not yet set to 202002L.
-            Also, the related defect reports <a href="https://wg21.link/cwg1496">DR1496</a> and
-            <a href="https://wg21.link/cwg1734">DR1734</a> are not yet implemented. Accordingly, deleted
-            special member functions are treated as eligible even though they shouldn't be.
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erichkeane wrote:

Those aren't implemented, and that IS true, but it is kind of orthogonal to concepts.  Those issues pre-date concepts, and are only somewhat more visible thanks to concepts, but are not 'worse' nor 'caused' by it.

https://github.com/llvm/llvm-project/pull/87998