Unify the Rspec options into fewer number of options

Current .rspec

$ cat .rspec 
--color

Current CLI options

$ git grep bundle.*rspec
doc/development/README.md:bundle exec rspec
gitlab-ci-config/dev-gitlab-org.yml:    - bundle exec rspec --color --format RspecJunitFormatter --out junit_ci_rspec.xml --format documentation ci_build_specs
gitlab-ci-config/gitlab-com.yml:    - bundle exec rake "knapsack:rspec[--color --format RspecJunitFormatter --out junit_rspec.xml --format documentation]"
gitlab-ci-config/gitlab-com.yml:    - bundle exec rspec --color --format RspecJunitFormatter --out junit_ci_rspec.xml --format documentation ci_build_specs