Update 256Concepts.html

Author: bertanimauro

docs/256Concepts.html

@@ -51,7 +51,7 @@
 
   var simulation = d3.forceSimulation(nodes)
     .force('charge', d3.forceManyBody().strength(-200))
-    .force('center', d3.forceCenter(width / 15, height / 15))
+    .force('center', d3.forceCenter(width / 5, height / 5))
     .force('link', d3.forceLink().links(links))
     .on('tick', ticked);