Removed API endpoint and specs

.codeclimate.yml

.rubocop_todo.yml

app/models/application_setting.rb

app/models/concerns/project_features_compatibility.rb

changelogs/unreleased/fj-36819-remove-v3-api.yml

doc/api/README.md

doc/api/applications.md

doc/api/environments.md

doc/api/projects.md

doc/api/v3_to_v4.md

doc/development/geo.md

doc/integration/shibboleth.md

ee/lib/api/v3/ldap_group_links.rb

ee/lib/api/v3/project_git_hook.rb

ee/lib/api/v3/project_push_rule.rb

ee/spec/requests/api/v3/builds_spec.rb

ee/spec/requests/api/v3/github_spec.rb

ee/spec/requests/api/v3/ldap_group_links_spec.rb

ee/spec/requests/api/v3/project_push_rule_spec.rb

lib/api/api.rb