HTTP Error 403 when downloading content from Udemy (JSON metadata)

[pleasemarkdarkly]

Checklist

• [ X] I'm reporting a broken site support issue
• [ ] I've verified that I'm running youtube-dl version 2021.06.06
• [ ] I've checked that all provided URLs are alive and playable in a browser
• [ ] I've checked that all URLs and arguments with special characters are properly quoted or escaped
• [ ] I've searched the bugtracker for similar bug reports including closed ones
• [ ] I've read bugs section in FAQ

Verbose log

[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'--verbose', u'--cookies', u'./cookies.txt', u'-F', u'-o', u'./videos/%(playlist)s/%(chapter_number)s - %(chapter)s/%(title)s.%(ext)s', u'https://www.udemy.com/course/blockchain-developer/learn/lecture/16947870']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2021.06.06
[debug] Python version 2.7.16 (CPython) - Darwin-20.5.0-x86_64-i386-64bit
[debug] exe versions: ffmpeg 4.4, ffprobe 4.4, rtmpdump 2.4
[debug] Proxy map: {}
[udemy:course] course: Downloading webpage
[udemy:course] 1172526: Downloading course curriculum
[download] Downloading playlist: 1172526
[udemy:course] playlist 1172526: Collected 121 video ids (downloading 121 of them)
[download] Downloading video 1 of 121
[udemy] 6846516: Downloading webpage
[udemy] 6846516: Downloading lecture JSON
[udemy] 6846516: Downloading lecture JSON
ERROR: Unable to download JSON metadata: HTTP Error 403: Forbidden (caused by HTTPError()); please report this issue on https://yt-dl.org/bug . Make sure you are using the latest version; type  youtube-dl -U  to update. Be sure to call youtube-dl with the --verbose flag and include its complete output.
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/common.py", line 634, in _request_webpage
    return self._downloader.urlopen(url_or_request)
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 2288, in urlopen
    return self._opener.open(req, timeout=self._socket_timeout)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 435, in open
    response = meth(req, response)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 548, in http_response
    'http', request, response, code, msg, hdrs)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 473, in error
    return self._call_chain(*args)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 407, in _call_chain
    result = func(*args)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 556, in http_error_default
    raise HTTPError(req.get_full_url(), code, msg, hdrs, fp)```

## Description

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Downloading Udemy course materials with username and password or cookie both return the above error. Emailing pretty@pleasemarkdarkly.com, I'll provide the cookie. 

[dirkf]

Same issue as #22306, closed as solved. See also #29705, #29410.