Dev fix some types (#29547)

The primary key is usually a bigint column, but the foreign key columns
are usually of integer type. This can lead to issues when joining these
columns due to mismatched types and different value ranges.

This was using a temporary plugin / test API to make tests pass. After
more careful consideration, we concluded that it is safe to alter the
tables directly.

spec/rails_helper.rb

@@ -476,9 +476,6 @@ RSpec.configure do |config|
       Capybara::Selenium::Driver.new(app, **mobile_driver_options)
     end
 
-    migrate_column_to_bigint(AllowedPmUser, :allowed_pm_user_id)
-    migrate_column_to_bigint(Bookmark, :bookmarkable_id)
-    migrate_column_to_bigint(IgnoredUser, :ignored_user_id)
     migrate_column_to_bigint(PostAction, :post_action_type_id)
     migrate_column_to_bigint(Reviewable, :target_id)
     migrate_column_to_bigint(ReviewableHistory, :reviewable_id)