Fix missing workflow sample chess image (#84)

Author: maximthomas

openidm-zip/src/main/resources/samples/workflow/workflow/chessboard.xhtml

@@ -21,7 +21,7 @@
 .grid tbody tr:nth-child(even) td:nth-child(odd) { background-color: #eee; }
 
 .piece {
-    background-image: url('http://svn.symfony-project.com/plugins/dmChessPlugin/web/images/piece/sprite.png');
+    background-image: url('https://raw.githubusercontent.com/OpenIdentityPlatform/OpenIDM/refs/heads/master/openidm-zip/src/main/resources/samples/workflow/workflow/sprite.png');
     width: 64px;
     height: 64px;