change the rocks booking date

Signed-off-by: Birgit Brecknell <b@brck.nl>

Foundation/Summit/2024/social-activities.html

@@ -81,7 +81,7 @@ <h4 style="padding-top:20px">A guided tour of The Rocks</h4>
         Birg will organise a guided tour of <a href="https://www.rockswalkingtours.com.au/walking-tour/">The Rocks</a>, which gives an account of Sydney's colonial heritage.
     </p>
     <p>
-        Bookings are required by <span class="highlight">20 September 2024</span>. Min group size 12. Max group size 20.
+        Bookings are required by <span class="highlight">30 September 2024</span>. Min group size 12. Max group size 20.
     </p>
     <p>
         <strong>When: </strong> Monday 14 Oct 2024, meet at 3:15pm, tour 3:30-5pm