DEV: drop readonly from flags custom type (#27960)

Drop readonly as it is causing problems with seed fu

db/migrate/20240714231226_duplicate_flags_custom_type_to_require_message.rb

@@ -4,8 +4,6 @@ class DuplicateFlagsCustomTypeToRequireMessage < ActiveRecord::Migration[7.0]
   def up
     add_column :flags, :require_message, :boolean, default: false, null: false
 
-    Migration::ColumnDropper.mark_readonly("flags", "custom_type")
-
     DB.exec <<~SQL
       UPDATE flags
       SET require_message = custom_type
@@ -13,7 +11,6 @@ class DuplicateFlagsCustomTypeToRequireMessage < ActiveRecord::Migration[7.0]
   end
 
   def down
-    Migration::ColumnDropper.drop_readonly("flags", "custom_type")
     remove_column :flags, :require_message
   end
 end