Bumps rubocop (and dependencies)

[vyper]

• [x] bumps rubocop from 1.22 to 1.36;
• [x] bumps rubocop-performance from 1.11 to 1.15;
• [x] bumps rubocop-rspec from 2.5 to 2.13;
• [x] fixes some news rules
  • [x] RSpec/VerifiedDoubles
  • [x] Gemspec/DeprecatedAttributeAssignment
  • [x] RSpec/VerifiedDoubleReference
  • [x] RSpec/NoExpectationExample
• [x] Fixes spec without correct expectations
• [x] removes ruby 2.5 from tests