Remove deprecated mambaforge installer in CI

[niketagrawal]

Closes #243

Rollback to using conda instead of mamba in the setup conda environment step in CI.

The documentation of the GitHub action setup-miniconda mentions that mamba support is experimental and that latest conda provides comparable performance.

[DominicDirkx]

Looks like the code is now passing the unit tests. Does anything remain to be tested before we merge?

[niketagrawal]

Looks like the code is now passing the unit tests. Does anything remain to be tested before we merge?

Yes, the warning for the deprecated mambaforge installer is no longer present. Also, the build and unit tests pass.

I notice that the step in the workflow responsible for caching the conda environment for subsequent runs is failing for Linux and Windows because the path where conda env is located on the runner and where the CI workflow looks for it to cache do not match. This is not related to changes in this PR, but due to changes on the end of conda.

I have added the fix and re-run the CI to test if the the conda environment is cached successfully at the end of the workflow.

[niketagrawal]

Conda cache step works as expected again after adding the above fix.