UserWarning when calling ListExternalRepositories

I saw this in the logs while reproducing frontend#1291 (closed):

/home/lucidiot/dev/ark/backend/arkindex/process/providers.py:137: UserWarning: Calling a `list()` method without specifying `get_all=True` or `iterator=True` will return a maximum of 20 items. Your query returned 20 of 65 items. See https://python-gitlab.readthedocs.io/en/v3.14.0/api-usage.html#pagination for more details. If this was done intentionally, then this warning can be supressed by adding the argument `get_all=False` to the `list()` call. (python-gitlab: /home/lucidiot/.virtualenvs/backend/lib/python3.10/site-packages/gitlab/client.py:976)
  return gl.projects.list(min_access_level=40, search=query)

We do only care about 20 items, so we can suppress that warning as suggested.