Cleanup usages of `JSON.parse` in specs

ee/spec/controllers/boards/issues_controller_spec.rb

ee/spec/controllers/boards/lists_controller_spec.rb

ee/spec/controllers/boards/milestones_controller_spec.rb

ee/spec/controllers/boards/users_controller_spec.rb

ee/spec/controllers/groups/boards_controller_spec.rb

ee/spec/controllers/groups/epic_issues_controller_spec.rb

ee/spec/controllers/groups/epics/notes_controller_spec.rb

ee/spec/controllers/groups/epics_controller_spec.rb

...ec/controllers/groups/issues_analytics_controller_spec.rb

ee/spec/controllers/operations_controller_spec.rb

ee/spec/controllers/projects/boards_controller_spec.rb

.../controllers/projects/managed_licenses_controller_spec.rb

...ec/controllers/projects/merge_requests_controller_spec.rb

ee/spec/controllers/projects/service_desk_controller_spec.rb

ee/spec/requests/api/epic_links_spec.rb

ee/spec/requests/api/epics_spec.rb

ee/spec/requests/api/project_approvals_spec.rb

...controllers/admin/application_settings_controller_spec.rb

spec/controllers/application_controller_spec.rb

spec/controllers/boards/issues_controller_spec.rb