add conda-remove-defaults to setup miniforge in CI

[mgovers]

Attempt to fix the warning about conda default channels cfr. https://github.com/PowerGridModel/power-grid-model/actions/runs/14050295856

Checks

• Await CI run - double-check that the warning was fixed

NOTE

The original warning was replaced by a new one, but that has to do with the internal implementation of the setup-miniconda@v3 action, which apparently doesn't explicitly remove the original defaults until at a later step in the pipeline cfr.
https://github.com/PowerGridModel/power-grid-model/actions/runs/14054021767/job/39349486685#step:3:344 and https://github.com/PowerGridModel/power-grid-model/actions/runs/14054021767/job/39349486685#step:3:344

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[TonyXiang8787]

@mgovers please paste the screenshot of new conda-forge build log to prove it works.

[mgovers]

@mgovers please paste the screenshot of new conda-forge build log to prove it works.

I did in the Note section in the description

In the current main, we get the deprecation warning. In this branch, we get a log that first adds the defaults implicitly (which triggers a new warning) and then removes the defaults again. This is setup-miniconda@v3's internal implementation and while suboptimal, it still proves that we migrated correctly.