This will change some `requirements.txt` of pyln-testing in a way that
it does not require different package version i.e. to `tests/requirements.txt`.
The reason for this is that users are not forced to hassle with pyenv
or virtualenv and could just use `--user`.
```bash
pip install --user -r tests/requirements.txt -r contrib/pyln-testing/requirements.txt
```
Changelog-None