Unpin udata version in setup.py

[maudetes]

Fix datagouv/data.gouv.fr#1328

In etalab/udata-gouvfr#626, the install_requires of setup.py used a pinned version of udata if defined.
It prevents installing udata-front with any other working udata versions.

It was meant to be used in the release instead of the udata.git.
However, the version used to build the udata-front release shouldn't be added as a fixed dep in install_requires udata-front, but should only be used to install deps.

The latest release is already used in CI by replacing the dep to udata.git git by udata.
We then apply

pip-compile requirements/udata.in --output-file=requirements/udata.pip
...
pip install -r requirements/udata.pip

We're correctly using the latest udata release at this point (#363).

Historically, udata wasn't pinned to a specific version (v3.1.3, v2.0.0 (see info > requires_dist)).

Thus, let's remove the udata pinned version in the install_requires in setup.py