Upgrade rubocop to 0.56.0 and rubocop-rspec to 1.25.1

Upgrade 2 gems:

rubocop from 0.52.1 to 0.56.0

• required for rubocop-rspec update
• changelogs:
  • https://github.com/bbatsov/rubocop/releases/tag/v0.53.0
  • https://github.com/bbatsov/rubocop/releases/tag/v0.54.0
  • https://github.com/bbatsov/rubocop/releases/tag/v0.55.0
  • https://github.com/bbatsov/rubocop/releases/tag/v0.56.0

rubocop-rspec from 1.22.1 to 1.25.1

• required for RSpec/Pending cop
• changelogs:
  • https://github.com/rubocop-rspec/rubocop-rspec/releases/tag/v1.22.2
  • https://github.com/rubocop-rspec/rubocop-rspec/releases/tag/v1.23.0
  • https://github.com/rubocop-rspec/rubocop-rspec/releases/tag/v1.24.0
  • https://github.com/rubocop-rspec/rubocop-rspec/releases/tag/v1.25.0
  • https://github.com/rubocop-rspec/rubocop-rspec/releases/tag/v1.25.1