Remove duplicate push and PR jobs in CI

[jonmaddock]

When pushing to branch with an associated PR, all jobs are duplicated for the push and pull_request events. Could we just run each job once?

[timothy-nunn]

Hi @jonmaddock,

I believe these jobs have a place in our CI. The PR jobs run the code in the state it will be post-merge (if the PR was merged into main this second). As such we have cases as follow:

Where the PR jobs fail (in this case, its because main is currently failing due to #3204). In my opinion, this is another tool to help us identify changes made since the 'branch off' of main that will interact with a feature branch to cause PROCESS to fail.