Refresh codemirror on show pull comment tab (#11100)

Fix #10975

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: John Olheiser <john.olheiser@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com>

web_src/js/index.js

@@ -1135,6 +1135,7 @@ async function initRepository() {
     $repoComparePull.find('button.show-form').on('click', function (e) {
       e.preventDefault();
       $repoComparePull.find('.pullrequest-form').show();
+      autoSimpleMDE.codemirror.refresh();
       $(this).parent().hide();
     });
   }