Fix state desync in ComboMarkdownEditor (#36625)

Fixes https://github.com/go-gitea/gitea/issues/24253

When a tasklist checkbox is clicked, the tasklist code [updates
`.raw-content` with latest server
data](7a8fe9eb37/web_src/js/markup/tasklist.ts (L73))
in the DOM after POSTing.

Then when "Edit" is clicked the ComboMarkdownEditor is shown with a
stale value from the previous edit session.

The fix makes it always read from `.raw-content`, no server
syncronization necessary because the value in `.raw-content` is the
latest from the server.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/js/features/repo-issue-edit.ts

@@ -97,11 +97,9 @@ async function tryOnEditContent(e: Event) {
     cancelButton.addEventListener('click', cancelAndReset);
     form.addEventListener('submit', saveAndRefresh);
   }
-
-  // FIXME: ideally here should reload content and attachment list from backend for existing editor, to avoid losing data
-  if (!comboMarkdownEditor.value()) {
-    comboMarkdownEditor.value(rawContent.textContent);
-  }
+  // when the content has changed on server side, there is no sync, and this page doesn't have the latest content,
+  // the editor still shows the old content, server will reject end user's submit by "data-content-version" check
+  comboMarkdownEditor.value(rawContent.textContent);
   comboMarkdownEditor.switchTabToEditor();
   comboMarkdownEditor.focus();
   triggerUploadStateChanged(comboMarkdownEditor.container);