Adds missing argument in E2E tests for #install_kubernetes_agent

What does this MR do and why?

!123454 (merged) introduced a new argument for install_kubernetes_agent and there were 2 specs that didn't get updated. The build passed for that MR because these 2 tests are set to be run in live environments only so it didn't run in that MR pipeline. This MR just updates those 2 specs to supply an agent_name.

How to set up and validate locally

Run the specs against Staging.

bundle exec rspec qa/specs/features/browser_ui/7_configure/auto_devops/create_project_with_auto_devops_spec.rb
bundle exec rspec qa/specs/features/ee/api/7_configure/kubernetes/kubernetes_agent_spec.rb

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.