Fix BackgroundMigration::BackfillWorkItemTypeIdForIssues
A retry mechanism is in place as we expect queries to timeout.
The wrong exception was rescued. Before we rescued only from
ActiveRecord::StatementTimeout
and now we also rescue
ActiveRecord::QueryCanceled
Related to the incident gitlab-com/gl-infra/production#6695 (closed)
Related to #338004 (closed)
Edited by Mario Celi