Fix build with RuboCop v0.44.1
Fix build with RuboCop v0.44.1

Disable Metrics/BlockLength for gemspec.

backus/rubocop-rspec,andyw8/rubocop-rspec,nevir/rubocop-rspec,andyw8/rubocop-rspec,bquorning/rubocop-rspec,backus/rubocop-rspec