Fix Rails/SaveBang offenses

What does this MR do and why?

This MR aims to solve the issue #220040 (closed)

File Change

• .rubocop_todo/rails/save_bang.yml
• spec/lib/backup/manager_spec.rb
• spec/lib/gitlab/analytics/cycle_analytics/records_fetcher_spec.rb
• spec/lib/gitlab/auth/ldap/user_spec.rb
• spec/lib/gitlab/auth/o_auth/user_spec.rb
• spec/lib/gitlab/auth/saml/user_spec.rb

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.