Specify rubocop-rspec version explicitly

Specifying rubocop-rspec version explicitly. The latest version (2.24.0) has breaking changes - https://github.com/rubocop/rubocop-rspec/releases/tag/v2.24.0

Split RSpec/FilePath into RSpec/SpecFilePathSuffix and RSpec/SpecFilePathFormat.

This issue blocks Release gitlab-experiment version 0.9.0 (!210 - merged)

Job: https://gitlab.com/gitlab-org/ruby/gems/gitlab-experiment/-/jobs/5130754342

Also it updates ruby version to 3.1.4 to align with GitLab

Closes #78 (closed)