[dropbox] fix regex (#2814)

Closes #2812
Authored by: zenerdi0de

yt_dlp/extractor/dropbox.py

@@ -56,8 +56,8 @@ class DropboxIE(InfoExtractor):
             else:
                 raise ExtractorError('Password protected video, use --video-password <password>', expected=True)
 
-        json_string = self._html_search_regex(r'InitReact\.mountComponent.+ "props":(.+), "elem_id"', webpage, 'Info JSON')
-        info_json = self._parse_json(json_string, video_id)
+        json_string = self._html_search_regex(r'InitReact\.mountComponent\(.*?,\s*(\{.+\})\s*?\)', webpage, 'Info JSON')
+        info_json = self._parse_json(json_string, video_id).get('props')
         transcode_url = traverse_obj(info_json, ((None, 'preview'), 'file', 'preview', 'content', 'transcode_url'), get_all=False)
         formats, subtitles = self._extract_m3u8_formats_and_subtitles(transcode_url, video_id)