Prevent `{ internal: true }` from being stored in the router

Forgotten followup to #23669 :grimacing:

If you went to an internal route (e.g. `/rails/info/routes`), you would
previously see the following in your logger:

```bash
Processing by Rails::InfoController#routes as HTML
  Parameters: {"internal"=>true}
  Rendering /Users/jon/code/rails/rails/railties/lib/rails/templates/rails/info/routes.html.erb within layouts/application
  Rendered collection of /Users/jon/code/rails/rails/actionpack/lib/action_dispatch/middleware/templates/routes/_route.html.erb [2 times] (10.5ms)
  Rendered /Users/jon/code/rails/rails/actionpack/lib/action_dispatch/middleware/templates/routes/_table.html.erb (2.5ms)
  Rendered /Users/jon/code/rails/rails/railties/lib/rails/templates/rails/info/routes.html.erb within layouts/application (23.5ms)
Completed 200 OK in 50ms (Views: 35.1ms | ActiveRecord: 0.0ms)
```

Now, with this change, you would see:

```bash
Processing by Rails::InfoController#routes as HTML
  Rendering /Users/jon/code/rails/rails/railties/lib/rails/templates/rails/info/routes.html.erb within layouts/application
  Rendered collection of /Users/jon/code/rails/rails/actionpack/lib/action_dispatch/middleware/templates/routes/_route.html.erb [2 times] (1.6ms)
  Rendered /Users/jon/code/rails/rails/actionpack/lib/action_dispatch/middleware/templates/routes/_table.html.erb (10.2ms)
  Rendered /Users/jon/code/rails/rails/railties/lib/rails/templates/rails/info/routes.html.erb within layouts/application (17.4ms)
Completed 200 OK in 44ms (Views: 28.0ms | ActiveRecord: 0.0ms)
```

1 files changed, 30 insertions, 0 deletions

diff --git a/actionpack/test/dispatch/routing_test.rb b/actionpack/test/dispatch/routing_test.rb
index ade4b0c381..75fdc9469f 100644
--- a/actionpack/test/dispatch/routing_test.rb
+++ b/actionpack/test/dispatch/routing_test.rb
@@ -4795,3 +4795,33 @@ class TestPathParameters < ActionDispatch::IntegrationTest
     assert_equal "/ar | /ar/about", @response.body
   end
 end
+
+class TestInternalRoutingParams < ActionDispatch::IntegrationTest
+  Routes = ActionDispatch::Routing::RouteSet.new.tap do |app|
+    app.draw do
+      get '/test_internal/:internal' => 'internal#internal'
+    end
+  end
+
+  class ::InternalController < ActionController::Base
+    def internal
+      head :ok
+    end
+  end
+
+  APP = build_app Routes
+
+  def app
+    APP
+  end
+
+  def test_paths_with_partial_dynamic_segments_are_recognised
+    get '/test_internal/123'
+    assert_equal 200, response.status
+
+    assert_equal(
+      { controller: 'internal', action: 'internal', internal: '123' },
+      request.path_parameters
+    )
+  end
+end