Update RuboCop to 0.93.1
Updates rubocop to 0.93.1 and rubocop-rspec to 1.44.1 because gitlab-styles 6.2.0 does not support for supporting Ruby 2.5 (cf. https://gitlab.com/gitlab-org/labkit-ruby/-/jobs/1179310464)
Follows up: !64 (merged)
Blocks !67 (merged) !66 (merged)
Closes #22 (closed)
Edited by Takuya Noguchi