docs: update progress sponsor message

Author: egil

docs/site/sponsors/progress-ad-2022-dark-mode.svg

@@ -4,7 +4,7 @@
   <div class="sideaffix">
     <div class="sponsor-highlight supported">
       <a href="https://www.telerik.com/blazor-ui?utm_source=egilhansen&utm_medium=cpm&utm_campaign=blazor-trial-readme-sponsored-message">
-        <img width="200" src="/sponsors/progress-blazor-2022-300x300.png" />
+        <img width="200" src="/sponsors/progress-blazor-2022-dec-300x300.png" />
       </a>
       <p>Premium sponsor: <a href="https://www.telerik.com/blazor-ui?utm_source=egilhansen&utm_medium=cpm&utm_campaign=blazor-trial-readme-sponsored-message" title="Progress Telerik">Progress Telerik</a>.</p>
     </div>