[clang][NFC] Add a test for CWG2685 (#95206)

I believe it has been implemented since D139837 "Implements CTAD for
aggregates P1816R0 and P2082R1", so this just claims we have already
supported it.

Plus an update on the dr status page.

Author: zyn0217

clang/test/CXX/drs/cwg26xx.cpp

@@ -225,6 +225,15 @@ void m() {
 }
 
 #if __cplusplus >= 202302L
+
+namespace cwg2685 { // cwg2685: 17
+template <class T>
+struct A {
+  T ar[4];
+};
+A a = { "foo" };
+}
+
 namespace cwg2687 { // cwg2687: 18
 struct S{
     void f(int);

clang/www/cxx_dr_status.html

@@ -15918,7 +15918,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/2685.html">2685</a></td>
     <td>C++23</td>
     <td>Aggregate CTAD, string, and brace elision</td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="full" align="center">Clang 17</td>
   </tr>
   <tr class="open" id="2686">
     <td><a href="https://cplusplus.github.io/CWG/issues/2686.html">2686</a></td>