[DRE-maint] Bug#1019731: Suggested fix

[Pirate Praveen]

Utkarsh suggested this change will fix this bug, we need to test it 
before we add to the gitlab package.

diff --git a/config/application.rb b/config/application.rb
index 249db9c6a6..e7481e12e1 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -234,6 +234,12 @@ class Application < Rails::Application
     config.active_record.has_many_inversing = false
     config.active_record.belongs_to_required_by_default = false

+ # Allow Gitlab::Diff::Position because it was disallowed
+ # with Rails 6.1.6.4 security update. Whilst they have
+ # re-added support for Symbol, they expect the projects
+ # to add the classes they need to be explicitly allowed.
+ config.active_record.yaml_column_permitted_classes = [Symbol, 
DateTime, Gitlab::Diff::Position]
+
     # Enable the asset pipeline
     config.assets.enabled = true