[ie/tiktok:user] Fix extractor

[bashonly]

Closes #3776
Supersedes #4996

Template

Before submitting a pull request make sure you have:

• At least skimmed through contributing guidelines including yt-dlp coding conventions
• Searched the bugtracker for similar pull requests
• Checked the code with flake8 and ran relevant tests

In order to be accepted and merged into yt-dlp each piece of code must be in public domain or released under Unlicense. Check all of the following options that apply:

• I am the original author of this code and I am willing to release it under Unlicense

What is the purpose of your pull request?

• Fix or improvement to an extractor (Make sure to add/update tests)