Removed obsolete DialogManager property. (#1127)

Co-authored-by: tracyboehrer <tracyboehrer@users.noreply.github.com>

Author: LeeParrishMSFT

libraries/bot-dialogs/src/main/java/com/microsoft/bot/dialogs/DialogContext.java

@@ -166,14 +166,6 @@ public TurnContextStateCollection getServices() {
         return services;
     }
 
-    /**
-     * Gets the current DialogManager for this dialogContext.
-     * @return The root dialogManager that was used to create this dialog context chain.
-     */
-    public DialogManager getDialogManager() {
-        return getContext().getTurnState().get(DialogManager.class);
-    }
-
     /**
      * Starts a new dialog and pushes it onto the dialog stack.
      * @param dialogId ID of the dialog to start.