refactor: rename switchSourcePosition method

Author: javier-godoy

src/main/java/com/flowingcode/vaadin/addons/demo/SplitLayoutDemo.java

@@ -63,7 +63,7 @@ public SplitLayoutDemo(Component demo, List<SourceCodeTab> tabs) {
     getContent().setSizeFull();
   }
 
-  public void switchSourcePosition(SourcePosition position) {
+  private void setSourcePosition(SourcePosition position) {
     if (!sourcePosition.equals(position)) {
       toggleSourcePosition();
     }