[MAINT] Update Conda in base env in conda-package workflow

[ndgrigorian]

This PR proposes updating the conda package in the base environment in the conda-package workflow

Also fixes mistakes/bugs in the workflow that led to conda-build and conda-index potentially not being installed in the base env, which with newer Conda versions, could break the builds/tests

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/2308/index.html

[coveralls]

coverage: 75.476%. remained the same — update-conda-in-workflow into master