Revert "Merge pull request #12990 from vipulnsward/remove_visualizer_param"

This reverts commit 5a19346d2855ecb1c791cdef3af92589566d00db, reversing
changes made to d82588ee4756b03025813b3997f4db171ee0fcdc.

This argument is being used in the view
https://github.com/rails/rails/blob/5a19346d2855ecb1c791cdef3af92589566d00db/actionpack/lib/action_dispatch/journey/visualizer/index.html.erb#L4

It is being set using the binding
https://github.com/rails/rails/blob/5a19346d2855ecb1c791cdef3af92589566d00db/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb#L108