exclude release-please GH actions workflow from CI tests

[m-jahn]

• issue: every PR triggers the GH Actions test workflow
• this includes the automatic PR from the release-please workflow, another GH action
• to exclude this from tests, we can add this line to the jobs: section of the main.yml file:

if: ${{ github.actor != 'github.actions[bot]' }}

or

if: ${{ github.actor != 'dependabot[bot]' }}

For info see: https://stackoverflow.com/questions/71679568/github-actions-ignore-or-exclude-dependabot-pull-requests
This would be useful for ALL SM pipelines!

[m-jahn]

• see new entry in MPUSP/snakemake-workflow-template@4d7b3a2
• contains if-statement that should exclude tests on PRs triggered by GH actions bot