Removing the declaration of protected solves an issue when running syskit browse and visiting the profiles.

This is the error that comes up if not:
tools/syskit/lib/syskit/instance_requirements.rb:721:in `method_missing': protected method `pushed_selections' called for Syskit::PlaceholderTask<Base::PoseSrv>:Syskit::InstanceRequirements (NoMethodError)