feat(destinations): the post-16 section, replacing the placeholder

The 'Post-16 destination data coming soon' note is deleted rather than
reworded: for a school with no sixth form the truthful statement is that
the question does not apply, and a placeholder there implies something is
missing. hasSixthForm and .sixthFormNote go with it — nothing else used them.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BvdDKvFFSZuMVDH5fEyTob

nextjs-app/components/school/SecondaryAdmissionsSection.tsx

@@ -15,7 +15,7 @@ import {
 } from './lastDistanceOffered';
 
 export function SecondaryAdmissionsSection({
-  admissions, admissionsHistory, admissionDistance, schoolInfo, hasSixthForm,
+  admissions, admissionsHistory, admissionDistance, schoolInfo,
 }: {
   /* Nullable for the same reason as the primary section: a school can have a
      published cut-off and no EES admissions row. */
@@ -23,7 +23,6 @@ export function SecondaryAdmissionsSection({
   admissionsHistory: SchoolAdmissions[];
   admissionDistance: SchoolAdmissionDistance | null;
   schoolInfo: School;
-  hasSixthForm: boolean;
 }) {
   const cutoff = describeCutoff(admissionDistance);
   // Moved with this section from SecondarySchoolDetailView, its only consumer.
@@ -112,11 +111,6 @@ export function SecondaryAdmissionsSection({
         </p>
       )}
 
-      {hasSixthForm && (
-        <div className={styles.sixthFormNote}>
-          This school has a sixth form (Post-16 provision). Post-16 destination data coming soon.
-        </div>
-      )}
     </section>
   );
 }