Update public/index.html

public/index.html

@@ -267,7 +267,7 @@
           <!-- Grid column -->
           <div class="col-lg-3 col-md-6 mb-lg-0 mb-5">
             <div class="avatar mx-auto">
-              <img src="./imgs/avatar/DieterUcklemann.jpeg" class="rounded-circle z-depth-1" width="150px">
+              <img src="./imgs/avatar/DieterUcklemann.png" class="rounded-circle z-depth-1" width="150px">
             </div>
             <h5 class="font-weight-bold mt-4 mb-3">Prof. Dr. Dieter Uckelmann</h5>
             <p class="text-uppercase blue-text"><strong>Lab Leader</strong></p>