Update requirements.txt

[melroy89]

Description

Package name changed from fake_useragent to fake-useragent. Disclaimer: I'm the maintainer.

Checklist

• [x] Check that the base branch is set to develop and not main.
• [x] Ensure that the documentation will be consistent with the code upon merging.
• [ ] Add a line or a few lines that check the new features added.
• [ ] Ensure that unit tests pass. If you don't have a premium proxy, some of the tests will be skipped. The tests that are run should pass without raising MaxTriesExceededException or other exceptions.

[arunkannawadi]

Thanks for this PR, and even more so for maintaining fake-useragent!