message: Fix the bug: Do not show clear button for file question if it is readonly,
diff: <label data-bind="css: question.koChooseFileClass, attr: {for: question.inputId}, text: question.chooseButtonCaption"></label>
  <span data-bind="css: question.koCss().noFileChosen, visible: !question.koHasValue(), text: question.noFileChosenCaption"></span>
  </div>
  - <!-- ko if: question.koHasValue -->
  + <!-- ko if: question.koHasValue() && !question.isReadOnly -->
  <button type="button" data-bind="css: question.cssClasses.removeButton, click: question.doclean, text: question.cleanButtonCaption"></button>
  <!-- /ko -->
  <div data-bind="foreach: question.koData, visible: question.koHasValue">
  <!-- /ko -->
  </span>
  </div>
  - <!-- ko if: question.koHasValue -->
  + <!-- ko if: question.koHasValue() && !question.isReadOnly -->
  <button type="button" data-bind="css: question.cssClasses.removeButtonBottom, click: question.doclean, text: question.cleanButtonCaption"></button>
  <!-- /ko -->
  </div>
  