barectf: remove poetry virtualenvs config modification

barectf: remove poetry virtualenvs config modification

virtualenvs.create is defined as:

  Create a new virtual environment if one doesn't already exist.
  Defaults to true.

Tox provides a virtualenv for the CI execution.

Hence we can remove this statement and default to True for this setting.

[1] https://python-poetry.org/docs/configuration/#virtualenvscreate-boolean

Reported-by: Philippe Proulx <pproulx@efficios.com>
Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>