We aren't using ActiveStorage, but Rails was including its routes
anyway.
In Rails 6.1 there will be an option to disable these routes [1], but
for now we're changing the line requiring "rails/all" to the values
generated by a new Rails application with the --skip-active-storage
flag.
[1] https://github.com/rails/rails/commit/3cf65bcb8
7496c1bcb9