Replacing provision-with-micromamba action with setup-micromamba action.

[sjayellis]

This PR is replacing the deprecated provision-with-micromamba action with the newer setup-micromamba action.

Updates follow the recommended migration steps from the provision-with-micromamba page.

Actions to update:

• [x] verify-ghas.yaml - conda-forge-dep
• [x] verify-ghas.yaml - conda-defaults-dep
• [x] cookiecutter ci.yaml - test