Remove namespace_storage_size_limit from ApplicationSettings

Remove the namespace_storage_size_limit from ApplicationSettings

Remove usage of the column !38108 (merged)
Remove db column !46676 (merged)
Remove ignore_column from ApplicationSetting.rb https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/models/application_setting.rb#L10 with %13.7

Edited Dec 14, 2020 by Pavel Shutsin