This is Part 2 of enabling repeatable builds on the 14.2-maint branch.
Part 1 (AIPCC-7026) removed the publish-wheels job overrides to allow GitLab releases to be created with graph.json files.
    
Once wheel releases are ready and available, we need to enable repeatable build mode for production collections to ensure builds use the pinned versions from the graph.json files rather than latest available versions.

Expected results:

    Production collections on 14.2-maint will use repeatable build mode, 
    ensuring consistent and reliable builds using pinned dependency versions.