Remove drag and drop from Tree doc (#9992)

Tree does not support drag and drop right now (see #9804).

documentation/components/components-tree.asciidoc

@@ -18,7 +18,6 @@ endif::web[]
 The [classname]#Tree# component allows a natural way to represent data that has hierarchical relationships.
 The user can drill down in the hierarchy by expanding items by clicking on the expand arrow, and likewise collapse items.
 [classname]#Tree# is a selection component that allows selecting items.
-It also supports drag and drop, so you can drag items to and from a tree, and drop them in the hierarchy.
 
 A typical use of the [classname]#Tree# component is for displaying a hierarchical menu, as illustrated in <<figure.components.tree>>, or for displaying file systems or hierarchical datasets.