Uses system path seperator in a situation where it shouldn't

[davidanthoff]

I ran Registrator.jl locally on Windows to tag a new package (not just a new release). Registrator.jl ended up adding a path to the root Registry.toml in the registry that read like path = "M\\MyPackage", i.e. it used backslash in the Registry.toml, where I assume it should use a single forward slash instead.