fix(copy-paste): fix message on clipboard clear (#1838)

* Clear clipboard function was calling utils to
  notify when the clipboard was cleared
* This produced a nil value error
* Replaced with notify

lua/nvim-tree/actions/fs/copy-paste.lua

@@ -132,7 +132,7 @@ end
 function M.clear_clipboard()
   clipboard.move = {}
   clipboard.copy = {}
-  utils.notify.info "Clipboard has been emptied."
+  notify.info "Clipboard has been emptied."
 end
 
 function M.copy(node)