[C23] Remove WG14 N2660 from the list of papers we track

This paper was a clarification paper that made no normative changes to
the wording, so we can lean on the C99 status for this.

Author: AaronBallman

clang/www/c_status.html

@@ -642,11 +642,6 @@ <h2 id="c2x">C23 implementation status</h2>
       <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2186.pdf">N2186</a></td>
       <td class="unknown" align="center">Unknown</td>
     </tr>
-    <tr>
-      <td>Clarifying the restrict Keyword v2</td>
-      <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2260.pdf">N2660</a></td>
-      <td class="unknown" align="center">Unknown</td>
-    </tr>
     <tr>
       <td>Harmonizing static_assert with C++</td>
       <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2265.pdf">N2665</a></td>