Which bash runner to use for entry point CI tests?

[truth-quark]

From #86, there's a suggestion regarding which bash test runner to use for um2nc entrypoints:

https://github.com/ACCESS-NRI/um2nc-standalone/blob/82/un2nc-ci-entry-test/.github/workflows/CI.yml#L96-L102

  - name: Entrypoint test of driver script
    shell: bash -l {0}
    run: esm1p5_convert_nc --help

  - name: Entrypoint test of um2netcdf script
    shell: bash -l {0}
    run: um2nc --help

@CodeGat suggested removing shell: bash -l {0} lines to use the default bash --noprofile --norc -eo pipefail {0} provided by GitHub. See https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsshell. It is not clear if this works with conda environments required for testing (part of the reason for using bash -l.

The first step in this task is testing if the GitHub default bash command works with conda.