Don't require compat bounds for package which don't exist

[giordano]

https://github.com/JuliaRegistries/General/pull/94736#issuecomment-1793420070 initially complained that I didn't have compat bounds on Printf, which is a stdlib but doesn't exist in the registry at the moment, so I added it in https://github.com/JuliaPhysics/Measurements.jl/pull/161, with the result that the package now is uninstallable in Julia v1.0-1.6 because Printf doesn't exist: https://github.com/JuliaPhysics/Measurements.jl/issues/162. I don't think automerge should suggest adding compat bounds on packages which don't exist in the registry in the first place.