Fix tests namespace pollution from entsoe and remove tests/init

[Marenz]

See EnergieID/entsoe-py#447 for details.
Example of the problem:

nox > mypy docs noxfile.py tests
Success: no issues found in 8 source files
nox > pylint src docs noxfile.py tests
************* Module tests
tests/__init__.py:1:0: F0010: error while code parsing: Unable to load file tests/__init__.py:
[Errno 2] No such file or directory: 'tests/__init__.py' (parse-error)

THis also removes the init file, as described in https://github.com/frequenz-io/rnd/issues/170

[Copilot]

Pull Request Overview

This PR fixes a namespace pollution issue caused by the entsoe-py dependency by restricting its version range to avoid problematic versions that introduce a conflicting tests package.

• Updated version constraint for entsoe-py dependency from < 0.8.0 to < 0.7.1
• Added explanatory comment linking to the upstream issue

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[florian-wagner-frequenz]

LGTM, thanks for the link describing what's going on and the PR to upstream.
I assume you will unpin it once the fix is merged upstream.

[Marenz]

Updated to also remove the tests/init file to avoid masking similar problems in the future.

https://github.com/frequenz-io/rnd/issues/170

[Marenz]

I assume you will unpin it once the fix is merged upstream.

That is def. the plan.

[Marenz]

A fixed version https://github.com/EnergieID/entsoe-py/releases/tag/V0.7.6 was released