add relnote for sql.Null[T]

doc/go1.22.html

@@ -70,6 +70,15 @@ Do not send CLs removing the interior tags from such phrases.
   TODO: complete this section
 </p>
 
+<dl id="database/sql"><dt><a href="/pkg/database/sql/">database/sql</a></dt>
+  <dd>
+    <p><!-- https://go.dev/issue/60370, CL 501700 -->
+      The new <a href="/pkg/database/sql/#Null"><code>Null[T]</code></a> type
+      provide a way to scan nullable columns for any column types.
+    </p>
+  </dd>
+</dl>
+
 <h2 id="ports">Ports</h2>
 
 <p>