[C11] Remove WG14 N1537 from the status page

This paper was a rewording of WG14 N1485, correcting terminology and
bringing the C11 feature slightly closer in line with the C++11
feature. There is nothing additional to be done or test to conform to
what was specified by WG14 N1537, so we'll remove the entry and lean on
N1485 to track status for atomics.

Author: AaronBallman

clang/www/c_status.html

@@ -599,11 +599,6 @@ <h2 id="c11">C11 implementation status</h2>
       <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1532.htm">N1532</a></td>
       <td class="full" align="center">Yes</td>
     </tr>
-    <tr>
-      <td>Synthesis re _Atomic</td>
-      <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1537.htm">N1537</a></td>
-      <td class="unknown" align="center">Unknown</td>
-    </tr>
     <tr>
       <td>Clarification for wide evaluation</td>
       <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1531.pdf">N1531</a></td>