fix charter extended to date (#579)

Author: shawna-slh

src/pages/explainer.astro

@@ -483,7 +483,7 @@ import ExplainerRespec from "@/components/respec/ExplainerRespec.astro";
 
     <section id="schedule">
         <h2>Schedule</h2>
-        <p>AG is currently <a href="https://www.w3.org/2023/11/ag-charter">chartered</a> through November 2025. The
+        <p>AG is currently <a href="https://www.w3.org/2023/11/ag-charter">chartered</a> through April 2026. The
             schedule through that time period is maintained at <a
                 href="https://www.w3.org/WAI/GL/wiki/WCAG_3_Timeline#Publication_Plan">WCAG 3 Timeline</a>.</p>
         <p>AG will continue to iterate within a single normative document with informative supporting documentation.
@@ -626,4 +626,4 @@ import ExplainerRespec from "@/components/respec/ExplainerRespec.astro";
     </section>
 </body>
 
-</html>
+</html>