BigBang product pre-check pipelines should not be running on master

Referenced issue job - https://repo1.dso.mil/platform-one/big-bang/bigbang/-/jobs/1850845

Specifically, the pre version job should only run for MR's - but the other pre check jobs can follow.

New MR to fix this - https://repo1.dso.mil/platform-one/big-bang/bigbang/-/merge_requests/213