Fix rubocop violations in audit events models

What does this MR do and why?

Fix all Rubocop violations in audit events models.

• Layout/ArgumentAlignment
• Layout/SpaceInsideParens
• Rails/InverseOf
• Rails/RedundantForeignKey
• RSpec/ContextWording
• RSpec/MissingFeatureCategory
• Style/GuardClause

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

1. Run the following command in Rails console to include todo items as well

   REVEAL_RUBOCOP_TODO=1 bundle exec rubocop ee/app/models/audit_events/ ee/spec/models/audit_events/

2. The command should return with no offence detected

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.