Remove commit-check Job and Replace With Conditional Job Execution

[CodeGat]

We currently have a commit-check job that gets the authour of the current head_ref. This is used by future jobs so that we don't run repro (or indeed other checks) if they were created by vars.GH_ACTIONS_BOT_GIT_USER_NAME.

This can be simplified, and make the job diagram more palatable, by just using conditional job execution on the repro-ci job. For example, instead of if: needs.commit-check.outputs.authourship != vars.GH_ACTIONS_BOT_GIT_USER_NAME, you can use something like if: github.event.pull_request.head.user.name != vars.GH_ACTIONS_BOT_GIT_USER_NAME.