Necessary Maintenance #19294
Update the SingleGen production fcls to include prodsingle_common_sbnd.fcl rather than prodsingle_sbnd_proj.fcl
The production fcls that use the SingleGen generator do so through prodsingle_sbnd_proj.fcl.
They should inherit from prodsingle_common_sbnd.fcl instead.
For this to happen, prodsingle_common_sbnd.fcl should be updated to minimise (or default value) the number of SingleGen overrides that it currently does.