Update RuboCop to 1.81.7 and fix style offenses

[ericproulx]

Update RuboCop to 1.81.7 and Fix Style Offenses

Summary

This PR updates RuboCop and related gems to their latest versions and fixes style offenses identified by the updated linter.

Changes

Dependency Updates

• RuboCop: 1.76.2 → 1.81.7
• rubocop-performance: 1.25.0 → 1.26.1
• rubocop-rspec: 3.6.0 → 3.8.0

Code Style Fixes

• Added blank lines after extend Forwardable declarations (RuboCop style requirement)
  • lib/grape/api.rb
  • lib/grape/api/instance.rb
  • lib/grape/middleware/stack.rb
  • lib/grape/util/cache.rb
• Added blank lines after module/class declarations in specs
  • spec/grape/api/deeply_included_options_spec.rb
  • spec/grape/api/nested_helpers_spec.rb
  • spec/grape/api_spec.rb
  • spec/grape/dsl/parameters_spec.rb
  • spec/grape/validations/params_documentation_spec.rb
  • spec/grape/validations_spec.rb
• Simplified destructuring pattern in spec/grape/validations/params_scope_spec.rb

RuboCop Todo Updates

• Regenerated .rubocop_todo.yml with RuboCop 1.81.7
• Reduced offense counts in several categories:
  • RSpec/RepeatedExampleGroupDescription: 10 → 8 offenses
  • RSpec/StubbedMock: 4 → 2 offenses
  • RSpec/SubjectStub: 118 → 32 offenses (significant improvement!)
  • RSpec/VerifiedDoubles: 22 → 20 offenses
• Added new exclusion for RSpec/LeakyLocalVariable (1 offense)

Impact

• No breaking changes: All changes are style-only
• Improved code quality: Reduced RuboCop offenses, particularly in RSpec specs
• Up-to-date tooling: Using latest RuboCop version with improved checks

Testing

• All existing tests should continue to pass
• RuboCop runs cleanly with the updated configuration