Fix remove file on initial comment (#20127)

Store the file uuid(which is returned by Gitea in the upload file
response) onto the file object, so it can be used for the remove feature
to specify this file.

Fix #20115

web_src/js/features/repo-legacy.js

@@ -300,6 +300,7 @@ async function onEditContent(event) {
         thumbnailHeight: 480,
         init() {
           this.on('success', (file, data) => {
+            file.uuid = data.uuid;
             fileUuidDict[file.uuid] = {submitted: false};
             const input = $(`<input id="${data.uuid}" name="files" type="hidden">`).val(data.uuid);
             $dropzone.find('.files').append(input);