ci: turn job names to snake case

[nikku]

Proposed Changes

Follows up on our recent move to turn job names to snake case.

Checklist

To ensure you provided everything we need to look at your PR:

• Brief textual description of the changes present
• Visual demo attached
• Steps to try out present, i.e. using the @bpmn-io/sr tool
• Related issue linked via Closes {LINK_TO_ISSUE} or Related to {LINK_TO_ISSUE}

[nikku]

Test failures are unrelated to this PR, cf. #148.