Remove internal options from query string of paths

Fixes #17057

I DRYed up `polymorphic_path` to use `polymorphic_url` (introduced in cfdda38088c95194c3d8bb2fedb70bc06e8fe2e0).
/cc @tenderlove 
Actually I think a better fix is just remove this `routing_type` option from here. We are already setting it to `:path` in the original implementation of `polymorphic_path`.