Remove ActiveStorage's deprecated configs

`config.active_storage.replace_on_assign_to_many` has been removed at b06252e
and `config.active_storage.silence_invalid_content_types_warning` at 0cf8444.

Author: sato11

activestorage/lib/active_storage/engine.rb

@@ -118,15 +118,6 @@ class Engine < Rails::Engine # :nodoc:
         ActiveStorage.content_types_allowed_inline = app.config.active_storage.content_types_allowed_inline || []
         ActiveStorage.binary_content_type = app.config.active_storage.binary_content_type || "application/octet-stream"
         ActiveStorage.video_preview_arguments = app.config.active_storage.video_preview_arguments || "-y -vframes 1 -f image2"
-
-        unless app.config.active_storage.silence_invalid_content_types_warning.nil?
-          ActiveStorage.silence_invalid_content_types_warning = app.config.active_storage.silence_invalid_content_types_warning
-        end
-
-        unless app.config.active_storage.replace_on_assign_to_many.nil?
-          ActiveStorage.replace_on_assign_to_many = app.config.active_storage.replace_on_assign_to_many
-        end
-
         ActiveStorage.track_variants = app.config.active_storage.track_variants || false
       end
     end