fix: modal size for lti content

- dialogClassName was working with Modal from paragon, but after paragon v23 upgrade. We replaced Modal with ModalDialog with which dialogClassName doesn't work.
  - So, replace dialogClassName with simple className to apply same styles.

Author: Muhammad Faraz Maqsood

src/courseware/course/sequence/Unit/ContentIFrame.jsx

@@ -76,7 +76,7 @@ const ContentIFrame = ({
       {modalOptions.isOpen
           && (
           <ModalDialog
-            dialogClassName="modal-lti"
+            className="modal-lti"
             onClose={handleModalClose}
             size={modalOptions.isFullscreen ? 'fullscreen' : 'md'}
             isOpen