Move Propshaft::Server middleware before ActionDispatch::Executor`

`ActionDispatch::Static` is only added if
`config.public_file_server.enabled` is true.

Author: rafaelfranca

lib/propshaft/railtie.rb

@@ -66,7 +66,7 @@ class Railtie < ::Rails::Railtie
     initializer "propshaft.assets_middleware", group: :all do |app|
       app.assets = Propshaft::Assembly.new(app.config.assets)
       if config.assets.server
-        app.middleware.insert_after ::ActionDispatch::Static, Propshaft::Server, app.assets
+        app.middleware.insert_before ::ActionDispatch::Executor, Propshaft::Server, app.assets
       end
     end