Fix broken link for p21 teaser

Author: jhellingsdata

index.html

@@ -86,7 +86,7 @@ <h3 class="card-title">Chart Tutorials: Vega-Lite</h3>
             <div class="card" onclick="location.href='p21.html';">
                 <h3 class="card-title">21 charts for 21 countries</h3>
                 <!-- <div class="card-chart" id="chartx"></div> -->
-                <img src="Charts/p21/C1_Population_World.png" alt="" style="width: 100%">
+                <img src="charts/p21/C1_Population_World.png" alt="" style="width: 100%">
                 <span class="card-date">May 2024</span>
                 <p class="card-text">World's 21 most populous countries, compared through a series a charts on five economic topics. These charts were produced for LSE's Growth Day 2024.
                 </p>