Remove unused params

Its used at https://github.com/rails/rails/blob/master/actionpack/lib/action_dispatch/journey/visualizer/index.html.erb#L4

It was reverted once at https://github.com/rails/rails/commit/b39b3652e166dd8914b031ebb2d1db046a2137d8

Would be better to add a comment indicating where that parameter is used.