Fix failing test

_adjustDialog should be called when the modal is first displayed to prevent it jumping position when the viewport is resized

js/src/modal.js

@@ -135,6 +135,8 @@ const Modal = (($) => {
       this._checkScrollbar()
       this._setScrollbar()
 
+      this._adjustDialog()
+
       $(document.body).addClass(ClassName.OPEN)
 
       this._setEscapeEvent()