remove logging library from ensembles module

[Zeitsperre]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes Disable logging in xclim.ensembles module? #1039
• Tests for the changes have been added (for bug fixes / features)
  • (If applicable) Documentation has been added / updated (for bug fixes / features)
• HISTORY.rst has been updated (with summary of main changes)
  • Link to issue (:issue:number) and pull request (:pull:number) has been added
• bumpversion patch has been called on this branch
• The relevant author information has been added to .zenodo.json

What kind of change does this PR introduce?

• replaces logger and logging call with warnings

Does this PR introduce a breaking change?

No.

Other information:

[Zeitsperre]

Click just released a new version that is incompatible with the newest black (psf/black#2964). A version addressing this is being tagged today.

[coveralls]

Coverage decreased (-0.002%) to 91.582% when pulling 694da2d on remove_ensembles_logging into 6eb9005 on master.

[aulemahal]

With removing the other one and an update to the history, this is good to go!

The only other logging xclim does is in utils.py but this one is controllable via xclim options, so no need to touch it to close the issue.